Patient selectable joint arthroplasty devices and surgical tools

ABSTRACT

Disclosed herein are methods, compositions and tools for repairing articular surfaces repair materials and for repairing an articular surface. The articular surface repairs are customizable or highly selectable by patient and geared toward providing optimal fit and function. The surgical tools are designed to be customizable or highly selectable by patient to increase the speed, accuracy and simplicity of performing total or partial arthroplasty.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 11/671,745 entitled“Patient Selectable Joint Arthroplasty Devices and Surgical Tools” filedFeb. 6, 2007, which in turn claims the benefit of: U.S. Ser. No.60/765,592 entitled “SURGICAL TOOLS FOR PERFORMING JOINT ARTHROPLASTY”filed Feb. 6, 2006; U.S. Ser. No. 60/785,168, entitled “SURGICAL TOOLSFOR PERFORMING JOINT ARTHROPLASTY” filed Mar. 23, 2006; and U.S. Ser.No. 60/788,339, entitled “SURGICAL TOOLS FOR PERFORMING JOINTARTHROPLASTY” filed Mar. 31, 2006.

U.S. Ser. No. 11/671,745 is also a continuation-in-part of U.S. Ser. No.11/002,573 for “SURGICAL TOOLS FACILITATING INCREASED ACCURACY, SPEEDAND SIMPLICITY IN PERFORMING JOINT ARTHROPLASTY” filed Dec. 2, 2004,which in turn is a continuation-in-part of U.S. Ser. No. 10/724,010 for“PATIENT SELECTABLE JOINT ARTHROPLASTY DEVICES AND SURGICAL TOOLSFACILITATING INCREASED ACCURACY, SPEED AND SIMPLICITY IN PERFORMINGTOTAL AND PARTIAL JOINT ARTHROPLASTY” filed Nov. 25, 2003.

Each of the above-described applications are hereby incorporated byreference in their entireties.

FIELD OF THE INVENTION

The present invention relates to orthopedic methods, systems andprosthetic devices and more particularly relates to methods, systems anddevices for articular resurfacing. The present invention also includessurgical molds designed to achieve optimal cut planes in a joint inpreparation for installation of a joint implant.

BACKGROUND OF THE INVENTION

There are various types of cartilage, e.g., hyaline cartilage andfibrocartilage. Hyaline cartilage is found at the articular surfaces ofbones, e.g., in the joints, and is responsible for providing the smoothgliding motion characteristic of moveable joints. Articular cartilage isfirmly attached to the underlying bones and measures typically less than5 mm in thickness in human joints, with considerable variation dependingon joint and site within the joint. In addition, articular cartilage isaneural, avascular, and alymphatic. In adult humans, this cartilagederives its nutrition by a double diffusion system through the synovialmembrane and through the dense matrix of the cartilage to reach thechondrocyte, the cells that are found in the connective tissue ofcartilage.

Adult cartilage has a limited ability of repair; thus, damage tocartilage produced by disease, such as rheumatoid and/or osteoarthritis,or trauma can lead to serious physical deformity and debilitation.Furthermore, as human articular cartilage ages, its tensile propertieschange. The superficial zone of the knee articular cartilage exhibits anincrease in tensile strength up to the third decade of life, after whichit decreases markedly with age as detectable damage to type II collagenoccurs at the articular surface. The deep zone cartilage also exhibits aprogressive decrease in tensile strength with increasing age, althoughcollagen content does not appear to decrease. These observationsindicate that there are changes in mechanical and, hence, structuralorganization of cartilage with aging that, if sufficiently developed,can predispose cartilage to traumatic damage.

For example, the superficial zone of the knee articular cartilageexhibits an increase in tensile strength up to the third decade of life,after which it decreases markedly with age as detectable damage to typeII collagen occurs at the articular surface. The deep zone cartilagealso exhibits a progressive decrease in tensile strength with increasingage, although collagen content does not appear to decrease. Theseobservations indicate that there are changes in mechanical and, hence,structural organization of cartilage with aging that, if sufficientlydeveloped, can predispose cartilage to traumatic damage.

Once damage occurs, joint repair can be addressed through a number ofapproaches. One approach includes the use of matrices, tissue scaffoldsor other carriers implanted with cells (e.g., chondrocytes, chondrocyteprogenitors, stromal cells, mesenchymal stem cells, etc.). Thesesolutions have been described as a potential treatment for cartilage andmeniscal repair or replacement. See, also, International Publications WO99/51719 to Fofonoff, published Oct. 14, 1999; WO01/91672 to Simon etal., published Dec. 6, 2001; and WO01/17463 to Mannsmann, published Mar.15, 2001; U.S. Pat. No. 6,283,980 B1 to Vibe-Hansen et al., issued Sep.4, 2001, U.S. Pat. No. 5,842,477 to Naughton issued Dec. 1, 1998, U.S.Pat. No. 5,769,899 to Schwartz et al. issued Jun. 23, 1998, U.S. Pat.No. 4,609,551 to Caplan et al. issued Sep. 2, 1986, U.S. Pat. No.5,041,138 to Vacanti et al. issued Aug. 29, 1991, U.S. Pat. No.5,197,985 to Caplan et al. issued Mar. 30, 1993, U.S. Pat. No. 5,226,914to Caplan et al. issued Jul. 13, 1993, U.S. Pat. No. 6,328,765 toHardwick et al. issued Dec. 11, 2001, U.S. Pat. No. 6,281,195 to Ruegeret al. issued Aug. 28, 2001, and U.S. Pat. No. 4,846,835 to Grandeissued Jul. 11, 1989. However, clinical outcomes with biologicreplacement materials such as allograft and autograft systems and tissuescaffolds have been uncertain since most of these materials cannotachieve a morphologic arrangement or structure similar to or identicalto that of normal, disease-free human tissue it is intended to replace.Moreover, the mechanical durability of these biologic replacementmaterials remains uncertain.

Usually, severe damage or loss of cartilage is treated by replacement ofthe joint with a prosthetic material, for example, silicone, e.g. forcosmetic repairs, or metal alloys. See, e.g., U.S. Pat. No. 6,383,228 toSchmotzer, issued May 7, 2002; U.S. Pat. No. 6,203,576 to Afriat et al.,issued Mar. 20, 2001; U.S. Pat. No. 6,126,690 to Ateshian, et al.,issued Oct. 3, 2000. Implantation of these prosthetic devices is usuallyassociated with loss of underlying tissue and bone without recovery ofthe full function allowed by the original cartilage and, with somedevices, serious long-term complications associated with the loss ofsignificant amount of tissue and bone can include infection, osteolysisand also loosening of the implant.

Further, joint arthroplasties are highly invasive and require surgicalresection of the entire or the majority of the articular surface of oneor more bones. With these procedures, the marrow space is reamed inorder to fit the stem of the prosthesis. The reaming results in a lossof the patient's bone stock. U.S. Pat. No. 5,593,450 to Scott et al.issued Jan. 14, 1997 discloses an oval domed shaped patella prosthesis.The prosthesis has a femoral component that includes two condyles asarticulating surfaces. The two condyles meet to form a second trochleargroove and ride on a tibial component that articulates with respect tothe femoral component. A patella component is provided to engage thetrochlear groove. U.S. Pat. No. 6,090,144 to Letot et al. issued Jul.18, 2000 discloses a knee prosthesis that includes a tibial componentand a meniscal component that is adapted to be engaged with the tibialcomponent through an asymmetrical engagement.

Another joint subject to invasive joint procedures is the hip. U.S. Pat.No. 6,262,948 to Storer et al. issued Sep. 30, 2003 discloses a femoralhip prosthesis that replaces the natural femoral head. U.S. PatentPublications 2002/0143402 A1 and 2003/0120347 to Steinberg publishedOct. 3, 2002 and Jun. 26, 2003, respectively, also disclose a hipprosthesis that replaces the femoral head and provides a member forcommunicating with the ball portion of the socket within the hip joint.

A variety of materials can be used in replacing a joint with aprosthetic, for example, silicone, e.g. for cosmetic repairs, orsuitable metal alloys are appropriate. See, e.g., U.S. Pat. No.6,443,991 B1 to Running issued Sep. 3, 2002, U.S. Pat. No. 6,387,131 B1to Miehlke et al. issued May 14, 2002; U.S. Pat. No. 6,383,228 toSchmotzer issued May 7, 2002; U.S. Pat. No. 6,344,059 B1 to Krakovits etal. issued Feb. 5, 1002; U.S. Pat. No. 6,203,576 to Afriat et al. issuedMar. 20, 2001; U.S. Pat. No. 6,126,690 to Ateshian et al. issued Oct. 3,2000; U.S. Pat. No. 6,013,103 to Kaufman et al. issued Jan. 11, 2000.Implantation of these prosthetic devices is usually associated with lossof underlying tissue and bone without recovery of the full functionallowed by the original cartilage and, with some devices, seriouslong-term complications associated with the loss of significant amountsof tissue and bone can cause loosening of the implant. One suchcomplication is osteolysis. Once the prosthesis becomes loosened fromthe joint, regardless of the cause, the prosthesis will then need to bereplaced. Since the patient's bone stock is limited, the number ofpossible replacement surgeries is also limited for joint arthroplasty.

As can be appreciated, joint arthroplasties are highly invasive andrequire surgical resection of the entire, or a majority of the,articular surface of one or more bones involved in the repair. Typicallywith these procedures, the marrow space is fairly extensively reamed inorder to fit the stem of the prosthesis within the bone. Reaming resultsin a loss of the patient's bone stock and over time subsequentosteolysis will frequently lead to loosening of the prosthesis. Further,the area where the implant and the bone mate degrades over timerequiring the prosthesis to eventually be replaced. Since the patient'sbone stock is limited, the number of possible replacement surgeries isalso limited for joint arthroplasty. In short, over the course of 15 to20 years, and in some cases even shorter time periods, the patient canrun out of therapeutic options ultimately resulting in a painful,non-functional joint.

A variety of tools are available to assist surgeons in performing jointsurgery. In the knee, for example, U.S. Pat. No. 4,501,266 to McDanielissued Feb. 26, 1985 discloses a knee distraction device thatfacilitates knee arthroplasty. The device has an adjustable forcecalibration mechanism that enables the device to accommodate controlledselection of the ligament-tensioning force to be applied to therespective, opposing sides of the knee. U.S. Pat. No. 5,002,547 toPoggie et al. issued Mar. 26, 1991 discloses a modular apparatus for usein preparing the bone surface for implantation of a modular total kneeprosthesis. The apparatus has cutting guides, templates, alignmentdevices along with a distractor and clamping instruments that providemodularity and facilitate bone resection and prosthesis implantation.U.S. Pat. No. 5,250,050 to Poggie et al. issued Oct. 5, 1993 is alsodirected to a modular apparatus for use in preparing a bone surface forthe implantation of a modular total knee prosthesis. U.S. Pat. No.5,387,216 to Thornhill et al. issued Feb. 7, 1995 disclosesinstrumentation for use in knee revision surgery. A bearing sleeve isprovided that is inserted into the damaged canal in order to take upadditional volume. The rod passes through the sleeve and is positionedto meet the natural canal of the bone. The rod is then held in a fixedposition by the bearing sleeve. A cutting guide can then be mounted onthe rod for cutting the bone and to provide a mounting surface for theimplant. U.S. Pat. No. 6,056,756 to Eng et al. issued May 2, 2000discloses a tool for preparing the distal femoral end for a prostheticimplant. The tool lays out the resection for prosthetic replacement andincludes a jack for pivotally supporting an opposing bone such that thejack raises the opposing bone in flexion to the spacing of the intendedprosthesis. U.S. Pat. No. 6,106,529 to Techiera issued Aug. 22, 2000discloses an epicondylar axis referencing drill guide for use inresection to prepare a bone end for prosthetic joint replacement. U.S.Pat. No. 6,296,646 to Williamson issued Oct. 2, 2001 discloses a systemthat allows a practitioner to position the leg in the alignment that isdirected at the end of the implant procedure and to cut both the femurand tibia while the leg is fixed in alignment. U.S. Pat. No. 6,620,168to Lombardi et al. issued Sep. 16, 2003 discloses a tool forintermedullary revision surgery along with tibial components.

U.S. Pat. No. 5,578,037 to Sanders et al. issued Nov. 26, 1996 disclosesa surgical guide for femoral resection. The guide enables a surgeon toresect a femoral neck during a hip arthroplasty procedure so that thefemoral prosthesis can be implanted to preserve or closely approximatethe anatomic center of rotation of the hip.

U.S. Pat. No. 6,206,927 to Fell, et al., issued Mar. 27, 2001, and U.S.Pat. No. 6,558,421 to Fell, et al., issued May 6, 2003, disclose asurgically implantable knee prosthesis that does not require boneresection. This prosthesis is described as substantially elliptical inshape with one or more straight edges. Accordingly, these devices arenot designed to substantially conform to the actual shape (contour) ofthe remaining cartilage in vivo and/or the underlying bone. Thus,integration of the implant can be extremely difficult due to differencesin thickness and curvature between the patient's surrounding cartilageand/or the underlying subchondral bone and the prosthesis.

Interpositional knee devices that are not attached to both the tibia andfemur have been described. For example, Platt et al. (1969) “MouldArthroplasty of the Knee,” Journal of Bone and Joint Surgery51B(1):76-87, describes a hemi-arthroplasty with a convex undersurfacethat was not rigidly attached to the tibia. Devices that are attached tothe bone have also been described. Two attachment designs are commonlyused. The McKeever design is a cross-bar member, shaped like a “t” froma top perspective view, that extends from the bone mating surface of thedevice such that the “t” portion penetrates the bone surface while thesurrounding surface from which the “t” extends abuts the bone surface.See McKeever, “Tibial Plateau Prosthesis,” Chapter 7, p. 86. Analternative attachment design is the Macintosh design, which replacesthe “t” shaped fin for a series of multiple flat serrations or teeth.See Potter, “Arthroplasty of the Knee with Tibial Metallic Implants ofthe McKeever and Macintosh Design,” Surg. Clins. Of North Am. 49(4):903-915 (1969).

U.S. Pat. No. 4,502,161 to Wall issued Mar. 5, 1985, describes aprosthetic meniscus constructed from materials such as silicone rubberor Teflon with reinforcing materials of stainless steel or nylonstrands. U.S. Pat. No. 4,085,466 to Goodfellow et al. issued Mar. 25,1978, describes a meniscal component made from plastic materials.Reconstruction of meniscal lesions has also been attempted withcarbon-fiber-polyurethane-poly (L-lactide). Leeslag, et al., Biologicaland Biomechanical Performance of Biomaterials (Christel et al., eds.)Elsevier Science Publishers B.V., Amsterdam. 1986. pp. 347-352.Reconstruction of meniscal lesions is also possible with bioresorbablematerials and tissue scaffolds.

However, currently available devices do not always provide idealalignment with the articular surfaces and the resultant joint congruity.Poor alignment and poor joint congruity can, for example, lead toinstability of the joint. In the knee joint, instability typicallymanifests as a lateral instability of the joint.

Thus, there remains a need for compositions for joint repair, includingmethods and compositions that facilitate the integration between thecartilage replacement system and the surrounding cartilage. There isalso a need for tools that increase the accuracy of cuts made to thebone in a joint in preparation for surgical implantation of, forexample, an artificial joint.

SUMMARY OF THE INVENTION

The present invention provides novel devices and methods for replacing aportion (e.g., diseased area and/or area slightly larger than thediseased area) of a joint (e.g., cartilage and/or bone) with anon-pliable, non-liquid (e.g., hard) implant material, where the implantachieves a near anatomic fit with the surrounding structures andtissues. In cases where the devices and/or methods include an elementassociated with the underlying articular bone, the invention alsoprovides that the bone-associated element achieves a near anatomicalignment with the subchondral bone. The invention also provides for thepreparation of an implantation site with a single cut, or a fewrelatively small cuts.

In one aspect, the invention includes a method for providing articularreplacement material, the method comprising the step of producingarticular replacement (e.g., cartilage replacement material) of selecteddimensions (e.g., size, thickness and/or curvature).

In another aspect, the invention includes a method of making cartilagerepair material, the method comprising the steps of (a) measuring thedimensions (e.g., thickness, curvature and/or size) of the intendedimplantation site or the dimensions of the area surrounding the intendedimplantation site; and (b) providing cartilage replacement material thatconforms to the measurements obtained in step (a). In certain aspects,step (a) comprises measuring the thickness of the cartilage surroundingthe intended implantation site and measuring the curvature of thecartilage surrounding the intended implantation site. In otherembodiments, step (a) comprises measuring the size of the intendedimplantation site and measuring the curvature of the cartilagesurrounding the intended implantation site. In other embodiments, step(a) comprises measuring the thickness of the cartilage surrounding theintended implantation site, measuring the size of the intendedimplantation site, and measuring the curvature of the cartilagesurrounding the intended implantation site. In other embodiments, step(a) comprises reconstructing the shape of healthy cartilage surface atthe intended implantation site.

In any of the methods described herein, one or more components of thearticular replacement material (e.g., the cartilage replacementmaterial) can be non-pliable, non-liquid, solid or hard. The dimensionsof the replacement material can be selected following intraoperativemeasurements. Measurements can also be made using imaging techniquessuch as ultrasound, MRI, CT scan, x-ray imaging obtained with x-ray dyeand fluoroscopic imaging. A mechanical probe (with or without imagingcapabilities) can also be used to select dimensions, for example anultrasound probe, a laser, an optical probe and a deformable material ordevice.

In any of the methods described herein, the replacement material can beselected (for example, from a pre-existing library of repair systems),grown from cells and/or hardened from various materials. Thus, thematerial can be produced pre- or post-operatively. Furthermore, in anyof the methods described herein the repair material can also be shaped(e.g., manually, automatically or by machine), for example usingmechanical abrasion, laser ablation, radiofrequency ablation,cryoablation and/or enzymatic digestion.

In any of the methods described herein, the articular replacementmaterial can comprise synthetic materials (e.g., metals, liquid metals,polymers, alloys or combinations thereof) or biological materials suchas stem cells, fetal cells or chondrocyte cells.

In another aspect, the invention includes a method of repairing acartilage in a subject, the method of comprising the step of implantingcartilage repair material prepared according to any of the methodsdescribed herein.

In yet another aspect, the invention provides a method of determiningthe curvature of an articular surface, the method comprising the step ofintraoperatively measuring the curvature of the articular surface usinga mechanical probe. The articular surface can comprise cartilage and/orsubchondral bone. The mechanical probe (with or without imagingcapabilities) can include, for example an ultrasound probe, a laser, anoptical probe and/or a deformable material.

In a still further aspect, the invention provides a method of producingan articular replacement material comprising the step of providing anarticular replacement material that conforms to the measurementsobtained by any of the methods of described herein.

In a still further aspect, the invention includes a partial or fullarticular prosthesis comprising a first component comprising a cartilagereplacement material; and an optional second component comprising one ormore metals, wherein said second component can have a curvature similarto subchondral bone, wherein said prosthesis comprises less than about80% of the articular surface. In certain embodiments, the first and/orsecond component comprises a non-pliable material (e.g., a metal, apolymer, a metal alloy, a solid biological material). Other materialsthat can be included in the first and/or second components includepolymers, biological materials, metals, metal alloys or combinationsthereof. Furthermore, one or both components can be smooth or porous (orporous coated) using any methods or mechanisms to achieve in-growth ofbone known in the art. In certain embodiments, the first componentexhibits biomechanical properties (e.g., elasticity, resistance to axialloading or shear forces) similar to articular cartilage. The firstand/or second component can be bioresorbable and, in addition, the firstor second components can be adapted to receive injections.

In another aspect, an articular prosthesis comprising an externalsurface located in the load bearing area of an articular surface,wherein the dimensions of said external surface achieve a near anatomicfit with the adjacent, underlying or opposing cartilage is provided. Theprosthesis can comprise one or more metals or metal alloys.

In yet another aspect, an articular repair system comprising (a)cartilage replacement material, wherein said cartilage replacementmaterial has a curvature similar to surrounding, adjacent, underlying oropposing cartilage; and (b) at least one non-biologic material, whereinsaid articular surface repair system comprises a portion of thearticular surface equal to, smaller than, or greater than, theweight-bearing surface that is provided. In certain embodiments, thecartilage replacement material is non-pliable (e.g., hardhydroxyapatite, etc.). In certain embodiments, the system exhibitsbiomechanical (e.g., elasticity, resistance to axial loading or shearforces) and/or biochemical properties similar to articular cartilage.The first and/or second component can be bioresorbable and, in addition,the first or second components can be adapted to receive injections.

In a still further aspect of the invention, an articular surface repairsystem comprising a first component comprising a cartilage replacementmaterial, wherein said first component has dimensions similar to that ofadjacent, surrounding, underlying or opposing cartilage; and a secondcomponent, wherein said second component has a curvature similar tosubchondral bone, wherein said articular surface repair system comprisesless than about 80% of the articular surface (e.g., a single femoralcondyle, tibia, etc.) is provided. In certain embodiments, the firstcomponent is non-pliable (e.g., hard hydroxyapatite, etc.). In certainembodiments, the system exhibits biomechanical (e.g., elasticity,resistance to axial loading or shear forces) and/or biochemicalproperties similar to articular cartilage. The first and/or secondcomponent can be bioresorbable and, in addition, the first or secondcomponents can be adapted to receive injections. In certain embodiments,the first component has a curvature and thickness similar to that ofadjacent, underlying, opposing or surrounding cartilage. The thicknessand/or curvature can vary across the implant material.

In a still further embodiment, a partial articular prosthesis comprising(a) a metal or metal alloy; and (b) an external surface located in theload bearing area of an articular surface, wherein the external surfacedesigned to achieve a near anatomic fit with the adjacent surrounding,underlying or opposing cartilage is provided.

Any of the repair systems or prostheses described herein (e.g., theexternal surface) can comprise a polymeric material, for exampleattached to said metal or metal alloy. Any of the repair systems can beentirely composed of polymer. Further, any of the systems or prosthesesdescribed herein can be adapted to receive injections, for example,through an opening in the external surface of said cartilage replacementmaterial (e.g., an opening in the external surface terminates in aplurality of openings on the bone surface). Bone cement, polymers,Liquid Metal, therapeutics, and/or other bioactive substances can beinjected through the opening(s). In certain embodiments, bone cement isinjected under pressure in order to achieve permeation of portions ofthe marrow space with bone cement. In addition, any of the repairsystems or prostheses described herein can be anchored in bone marrow orin the subchondral bone itself. One or more anchoring extensions (e.g.,pegs, pins, etc.) can extend through the bone and/or bone marrow.

In any of the embodiments and aspects described herein, the joint can bea knee, shoulder, hip, vertebrae, elbow, ankle, wrist etc.

In another aspect, a method of designing an articular implant comprisingthe steps of obtaining an image of a joint, wherein the image includesboth normal cartilage and diseased cartilage; reconstructing dimensionsof the diseased cartilage surface to correspond to normal cartilage; anddesigning the articular implant to match the dimensions of thereconstructed diseased cartilage surface or to match an area slightlygreater than the diseased cartilage surface is provided. The image canbe, for example, an intraoperative image including a surface detectionmethod using any techniques known in the art, e.g., mechanical, optical,ultrasound, and known devices such as MRI, CT, ultrasound, digitaltomosynthesis and/or optical coherence tomography images. In certainembodiments, reconstruction is performed by obtaining a surface thatfollows the contour of the normal cartilage. The surface can beparametric and include control points that extend the contour of thenormal cartilage to the diseased cartilage and/or a B-spline surface. Inother embodiments, the reconstruction is performed by obtaining a binaryimage of cartilage by extracting cartilage from the image, whereindiseased cartilage appears as indentations in the binary image; andperforming, for example, a morphological closing operation (e.g.,performed in two or three dimensions using a structuring element and/ora dilation operation followed by an erosion operation) to determine theshape of an implant to fill the areas of diseased cartilage.

In yet another aspect, described herein are systems for evaluating thefit of an articular repair system into a joint, the systems comprisingone or more computing means capable of superimposing a three-dimensional(e.g., three-dimensional representations of at least one articularstructure and of the articular repair system) or a two-dimensionalcross-sectional image (e.g., cross-sectional images reconstructed inmultiple planes) of a joint and an image of an articular repair systemto determine the fit of the articular repair system. The computing meanscan be: capable of merging the images of the joint and the articularrepair system into a common coordinate system; capable of selecting anarticular repair system having the best fit; capable of rotating ormoving the images with respect to each other; and/or capable ofhighlighting areas of poor alignment between the articular repair systemand the surrounding articular surfaces. The three-dimensionalrepresentations can be generated using a parametric surfacerepresentation.

In yet another aspect, surgical tools for preparing a joint to receivean implant are described, for example a tool comprising one or moresurfaces or members that conform at least partially to the shape of thearticular surfaces of the joint (e.g., a femoral condyle and/or tibialplateau of a knee joint). In certain embodiments, the tool comprisesLucite silastic and/or other polymers or suitable materials. The toolcan be re-useable or single-use. The tool can be comprised of a singlecomponent or multiple components. In certain embodiments, the toolcomprises an array of adjustable, closely spaced pins. In anyembodiments described herein, the surgical tool can be designed tofurther comprise an aperture therein, for example one or more apertureshaving dimensions (e.g., diameter, depth, etc.) smaller or equal to oneor more dimensions of the implant and/or one or more apertures adaptedto receive one or more injectables. Any of the tools described hereincan further include one or more curable (hardening) materials orcompositions, for example that are injected through one or moreapertures in the tool and which solidify to form an impression of thearticular surface.

In still another aspect, a method of evaluating the fit of an articularrepair system into a joint is described herein, the method comprisingobtaining one or more three-dimensional images (e.g., three-dimensionalrepresentations of at least one articular structure and of the articularrepair system) or two-dimensional cross-sectional images (e.g.,cross-sectional images reconstructed in multiple planes) of a joint,wherein the joint includes at least one defect or diseased area;obtaining one or more images of one or more articular repair systemsdesigned to repair the defect or diseased area; and evaluating theimages to determine the articular repair system that best fits thedefect (e.g., by superimposing the images to determine the fit of thearticular repair system into the joint). In certain embodiments, theimages of the joint and the articular repair system are merged into acommon coordinate system. The three-dimensional representations can begenerated using a parametric surface representation. In any of thesemethods, the evaluation can be performed by manual visual inspectionand/or by computer (e.g., automated). The images can be obtained, forexample, using a C-arm system and/or radiographic contrast.

In yet another aspect, described herein is a method of placing animplant into an articular surface having a defect or diseased area, themethod comprising the step of imaging the joint using a C-arm systemduring placement of the implant, thereby accurately placing the implantinto a defect or diseased area.

Also disclosed is a customizable, or patient specific, implantconfigured for placement between joint surfaces formed by inserting ahollow device having an aperture and a lumen into a target joint, andinjecting material into the hollow device to form an implant.

A customizable, or patient specific, implant configured for placementbetween joint surfaces is also disclosed wherein the implant is formedby inserting a retaining device that engages at least a portion of onejoint surface in a joint and injecting material into an aperture of theretaining device to form an implant.

The invention is also directed to tools. In accordance with anotherembodiment of the invention, a surgical tool includes a template. Thetemplate has at least one contact surface for engaging a surfaceassociated with a joint. The at least one contact surface substantiallyconforms with the surface. The template further includes at least oneguide aperture for directing movement of a surgical instrument.

In accordance with related embodiments of the invention, the surface maybe an articular surface, a non-articular surface, a cartilage surface, aweight bearing surface, a non-weight surface and/or a bone surface. Thejoint has a joint space, with the surface either within the joint spaceor external to the joint space. The template may include a mold. Thetemplate may include at least two pieces, the at least two piecesincluding a first piece that includes one or more of the at least onecontact surfaces, the second piece including one or more of the at leastone guide apertures or guide surfaces. The at least one contact surfacemay include a plurality of discrete contact surfaces.

In accordance with further related embodiments of the invention, thecontact surface may be made of a biocompatible material, such asacylonitrile butadiene styrene, polyphenylsulfone, and polycarbonate.The contact surface may be capable of heat sterilization withoutdeforming. For example, the contact surface may be capable of heatsterilization without deforming at temperatures lower than 207 degreesCelsius, such as a contact surface made of polyphenylsulfone. Thecontact surface may be substantially transparent or semi-transparent,such as a contact surface made of Somos 11120.

In still further embodiments of the invention, the template may includea reference element, such as a pin or aiming device, for establishing areference plane relative to at least one of a biomechanical axis and ananatomical axis of a limb. In other embodiments, the reference elementmay be used for establishing an axis to assist in correcting an axisdeformity.

In accordance with another embodiment of the invention, a method ofjoint arthroplasty is provided. The method includes obtaining an imageof a joint, wherein the image includes a surface associated with ajoint. A template is created having at least one contact surface thatconforms with the surface. The template includes at least one guideaperture or guide surface or element for directing movement of asurgical instrument. The template is positioned such that the contactsurface abuts the surface in a predefined orientation.

In related embodiments of the invention, the joint surface is at leastone of an articular surface, a non-articular surface, a cartilagesurface, a weight bearing surface, a non-weight bearing surface, and abone surface. The joint has a joint space, wherein the surface may bewithin the joint space or external to the joint space. The at least onecontact surface may include a plurality of discrete contact surfaces.Creating the template may include rapid prototyping, milling and/orcreating a mold, the template furthermore may be sterilizable and/orbiocompatible. The rapid prototyping may include laying down successivelayers of plastic. The template may be a multi-piece template. Themulti-piece template may include a first piece that includes one or moreof the at least one contact surfaces, and a second piece that includesone or more of the at least one guide apertures or guide surface orelement. Obtaining the image may include determining dimensions of boneunderlying the cartilage, and adding a predefined thickness to the bonedimensions, the predefined thickness representing the cartilagethickness. Adding the predefined thickness may be a function of at leastone of an anatomic reference database, an age, a gender, and racematching. Obtaining the imaging may include performing an opticalimaging technique, an ultrasound, a CT, a spiral CT, and/or an MRI.

In further related embodiments of the invention, the method may furtherinclude anchoring the contact surface to the cartilage. The anchoringmay include using at least one of k-wire and adhesive. The anchoring mayinclude drilling a bit through the cartilage, and leaving the bit inplace. The anchoring may include forming the template to normal jointsurface, arthritic joint surface or the interface between normal andarthritic joint surface or combinations thereof.

In still further related embodiments of the invention, the template mayinclude a reference element. The method may include establishing, viathe reference element, a reference plane relative to at least one of anaxis and a anatomical axis of a limb. The biomechanical axis may extendfrom a center of a hip to a center of an ankle. Alternatively, an axismay be established via the reference element that is used to alignsurgical tools in correcting an axis deformity.

In further related embodiments of the invention, the method furtherincludes performing at least one of a muscle sparing technique and abone sparing technique. An incision for inserting the template may beequal to or less than one of 15 cm, 13 cm, 10 cm, 8 cm, and 6 cm. Atleast a portion of the template may be sterilized. Sterilizing mayinclude heat sterilization and/or sterilization using gas. Thesterilized portion may includes a mold.

In accordance with another embodiment of the invention, a surgical toolincludes a template. The template has at least one contact surface forengaging a surface associated with a joint, the at least one contactsurface substantially conforming with the surface. The contact surfaceis optionally substantially transparent or semi-transparent. Thetemplate further includes at least one guide aperture for directingmovement of a surgical instrument.

In accordance with another embodiment of the invention, a method ofjoint arthroplasty is presented. The method includes obtaining an imageassociated with a joint. A template is created having at least onecontact surface that conforms with a surface associated with the joint,the template including a reference element and at least one guideaperture or guide surface or element for directing movement of asurgical instrument. The template is aligned in an orientation on thejoint such that the reference element establishes a reference planerelative to a biomechanical axis of a limb. The template is anchored tothe joint such that the contact surface abuts the joint in saidorientation. The biomechanical axis may extend, for example, from acenter of a hip to a center of an ankle.

In accordance with another embodiment of the invention, a method ofjoint arthroplasty includes obtaining an image of a joint. A template iscreated having at least one contact surface that conforms with a surfaceassociated with the joint, the template including a reference elementand at least one guide aperture or guide surface or element fordirecting movement of a surgical instrument, the template including areference element. The template is aligned in an orientation on thesurface such that the reference element establishes an axis. Thetemplate may be anchored to the surface. A surgical tool is alignedusing the reference element to correct an axis deformity.

In accordance with another embodiment of the invention, a surgical toolincludes a template. The template includes a mold having at least onecontact surface for engaging a surface associated with a joint. The atleast one contact surface substantially conforms with the surface. Themold is made of a biocompatible material. The template further includesat least one guide aperture or guide surface or guide element fordirecting movement of a surgical instrument. The mold may besterilizable and/or substantially transparent or semi-transparent.

In accordance with still another embodiment of the invention, a surgicaltool includes a template. The template includes a mold having at leastone contact surface for engaging a joint surface. The at least onecontact surface substantially conforms with the joint surface. The moldis made of a biocompatible material. Furthermore, the mold is capable ofheat sterilization without deforming. The template includes at least oneguide aperture or guide surface or guide element for directing movementof a surgical instrument.

In accordance with related embodiments of the invention, the mold may becapable of heat sterilization without deformation. The contact surfacemay be made of polyphenylsulfone.

In accordance with another embodiment of the invention, a method ofusing a surgical tool is presented. The surgical tool includes a firsttemplate removably attached to a second template. The method includesanchoring the first template to a femoral joint surface, the firsttemplate having a first contact surface for engaging the femoral jointsurface. The second template is anchored to a tibial joint surface, thesecond template having a second contact surface for engaging a tibialjoint surface. After anchoring the first template and the secondtemplate, the second template is released from the first template, suchthat the second template is capable of moving independent of the firsttemplate.

In accordance with related embodiments of the invention, the method mayfurther include using the second template to direct a surgical cut onthe tibia. Anchoring the second template may occur subsequent or priorto anchoring the first template. At least one of the first and secondtemplates may include a mold. The first contact surface maysubstantially conform with the femoral joint surface. The second contactsurface may substantially conform with the tibial joint surface.

In accordance with another embodiment of the invention, a method ofperforming joint arthroplasty includes obtaining a first imageassociated with a first joint, obtaining a second image of a secondjoint, and optionally obtaining a third image of a third joint. Abiomechanical axis associated with the first joint and the second jointand optionally the third joint is determined. A template is provided forenabling surgery to correct an anatomic abnormality associated with atleast one of the first, second and/or third joint.

In another embodiment, gait, loading and other physical activities aswell as static positions of a joint may be simulated using a computerworkstation. The template and the resultant surgical procedures, e.g.cuts, drilling, rasping, can be optimized using this information toachieve an optimal functional result. For example, the template and theresultant implant position may be optimized for different degrees offlexion and extension, internal or external rotation, abduction oradduction. Thus, the templates may be used to achieve motion that isoptimized in one, two or more directions.

In accordance with related embodiments of the invention, the templatemay include at least one contact surface for engaging a surfaceassociated with the first joint, the second joint and/or the thirdjoint, the at least one contact surface substantially conforming withthe surface. The template may include at least one guide aperture orguide surface or guide element for directing movement of a surgicalinstrument.

In further related embodiments of the invention, obtaining the firstimage may include imaging one of at least 5 cm, at least 10 cm, at least15 cm, at least 20 cm, at least 25 cm, at least 30 cm, and at least 35cm beyond the first joint. Obtaining the first image/and or second imageand/or the third image may include performing a CT or an MRI. Performingthe MRI may include obtaining a plurality of MRI scans. Optionally, twoor more imaging modalities can be used and information obtained from theimaging modalities can be combined.

In accordance with another embodiment of the invention, a method ofperforming joint arthroplasty includes obtaining a computer image of asurface associated with a first joint. At least one deformity seen inthe computer image is removed pertaining to the surface, so as to forman improved anatomic or functional result. The at least one deformity isremoved from the surface to create a modified surface. A template isprovided based, at least in part, on the removal of the deformity. Thetemplate includes at least one contact surface for engaging the modifiedsurface, the at least one contact surface substantially conforming withthe modified surface.

In accordance with another embodiment of the invention, a method ofperforming joint arthroplasty includes obtaining a computer image of asurface associated with a first joint. At least one deformity seen inthe computer image is removed such as a biomechanical or anatomical axisdeformity, so as to form an improved anatomic or functional result. Theat least one deformity is removed in the surgical planning by modifyingthe shape or position of a template including the shape and/or positionof guide apertures, guide surface or guide elements. A template isprovided based, at least in part, on the removal of the deformity. Thetemplate includes at least one contact surface for engaging the jointsurface. The shape and/or position of guide apertures, guide surface orguide elements is selected or designed to achieve a correction of thedeformity.

In accordance with related embodiments of the invention, the templatemay be used in a surgical procedure. The template may include at leastone guide aperture, guide surface or guide elements, the method furtherincluding using the at least one guide aperture, guide surface or guideelements to direct movement of a surgical instrument. The at least onedeformity may include a osteophyte, a subchondral cyst, and/or anarthritic deformation.

In accordance with another embodiment of the invention, a method ofperforming joint arthroplasty includes obtaining an image of a surfaceassociated with a first joint, the image including at least onedeformity. A template is provided, based at least in part on the image,the template having at least one contact surface for engaging portionsof the surface free of the deformity. The at least one contact surfacesubstantially conforms with the portions of the surface. The template isused in a surgical procedure.

In accordance with related embodiments of the invention, the templatemay include at least one guide aperture, guide surface or guideelements, the method further including using the at least one guideaperture, guide surface or guide elements to direct movement of asurgical instrument. The at least one deformity may include aosteophyte, a subchondral cyst, and/or an arthritic deformation.

In accordance with another embodiment of the invention, a method ofperforming joint arthroplasty includes obtaining an image of a surfaceassociated with a joint, the image including at least subchondral bone.A template is provided, based at least in part on the image. Thetemplate includes at least one contact surface substantially conformingwith the subchondral bone. Residual cartilage is removed from thesurface in areas where the at least one contact surface is to contactthe subchondral bone. The template is positioned such that the at leastone contact surface abuts the subchondral bone in a predefinedorientation.

In accordance with another embodiment of the invention, a method ofperforming joint arthroplasty includes providing a template. Thetemplate is fixated to bone associated with a joint without performingany cuts to the joint. The template may be used in a surgical procedure.

In accordance with related embodiments of the invention, fixating mayinclude drilling into the bone and leaving a drill bit in the bone. Animage of a surface associated with a joint may be obtained, the templatehaving at least one contact surface that conforms with the surface.

Another tool is disclosed that is formed at least partially in situ andcomprises: a mold formed in situ using at least one of an inflatablehollow device or a retaining device to conform to the joint surface onat least one surface having a surface for engaging a joint surface; ablock that communicates with the mold; and at least one guide aperturein the block.

A method of placing an implant into a joint is also provided. The methodcomprises the steps of imaging the joint using a C-arm system, obtaininga cross-sectional image with the C-arm system, and utilizing the imagefor placing the implant into a joint.

In accordance with another embodiment of the invention, a system forjoint arthroplasty includes a first template. The first templateincludes at least one surface for engaging a first surface of a joint,the surface being a mirror image of portions or all of the firstsurface. The first template further includes at least one guide fordirecting movement of a surgical instrument. A linkage cross-referencesat least one surgical tool relative to said guide and relative to one ofan anatomical and a biomechanical axis.

In accordance with related embodiments of the invention, the surgicaltool may be a second template, the second template including at leastone guide for directing movement of a surgical instrument. The secondtemplate may include a surface that is a mirror image of a secondsurface of the joint. The second joint surface may oppose the firstjoint surface. At least one guide of the second template may direct thesurgical instrument in at least one of a cut, a milling, and a drillingoriented in a predefined location relative to said first template andadapted in shape, size or orientation to an implant shape. The shapeand/or position of the at least one guide of the first template may bebased, at least in part, on one or more axis related to said joint. Thelinkage may be an attachment mechanism, which may cause the firsttemplate to directly contact the at least one surgical tool, oralternatively, attaches the first template and the at least one surgicaltool such that the first template and the at least one surgical tool donot directly contact each other. The linkage may allow for rotationrelative to one of an anatomical and a biomechanical axis. The firsttemplate may include a removably attached block, the block including theat least one guide of the first template.

In accordance with another embodiment of the invention, a system forjoint arthroplasty is presented that includes a first template. Thefirst template includes at least one surface for engaging a firstsurface of a joint, the surface being a mirror image of portions or allof the first surface. The first template further includes at least oneguide for directing movement of a surgical instrument. A linkagecross-references at least one surgical tool on a second surface of thejoint opposing the first surface.

In accordance with another embodiment of the invention, a system forjoint arthroplasty is presented that includes a first template. Thefirst template includes at least one first template surface for engaginga first surface of a joint, the first template surface being a mirrorimage of portions or all of the first surface. The first templatefurther includes at least one guide for directing movement of a surgicalinstrument. A second template includes at least one second templatesurface for engaging a second surface of a joint, the second templatebeing a mirror image of portions or all of the second surface. Thesecond template further includes at least one guide for directingmovement of a surgical instrument. A linkage cross-references the firsttemplate and the second template.

In accordance with another embodiment of the invention, a system forjoint arthroplasty includes a first template. The first templateincludes at least one surface for engaging a first surface of a joint,the surface being a mirror image of portions or all of the firstsurface. The first template further includes at least one guide fordirecting movement of a surgical instrument. A linkage cross-referencesat least one surgical tool, wherein the linkage allows for rotationrelative to one of an anatomical and a biomechanical axis.

In accordance with another embodiment of the invention, a method ofjoint arthroplasty includes positioning at least one contact surface ofa first template onto a first surface of a joint. A second template iscross-referenced to the first template to align position of the secondtemplate on a second surface of the joint, the second template includingat least one guide. Movement of the surgical instrument is directedusing the at least one guide of the second template relative to saidguide and relative to one of an anatomical and a biomechanical axis.

In accordance with related embodiments of the invention, the at leastone contact surface of the first template is substantially a mirrorimage of the first surface. The method may further include obtainingelectronic image data of the joint, and determining a shape of the atleast one contact surface of the first template based, at least in part,on electronic image data.

In accordance with other related embodiments of the invention, themethod may further include, prior to directing movement of the surgicalinstrument, positioning at least one contact surface of the secondtemplate to the second joint surface. The at least one contact surfaceof the second template may be substantially a mirror image of the secondsurface. The method may further include obtaining electronic image dataof the joint, and determining a shape of the at least one contactsurface of the second template based, at least in part, on electronicimage data.

In accordance with yet further related embodiments of the invention,cross-referencing the second template to the first template may includesattaching the second template to the first template. Attaching thesecond template to the first template may include performingintraoperative adjustments. The second template is attached to the firsttemplate via a pin, and wherein performing intraoperative adjustmentsincludes rotating the second template around the pin. The method mayfurther include performing an intraoperative adjustment on the positionof the second template on the second surface of the joint, whereinperforming the intraoperative adjustment includes using one of spacers,ratchets, and telescoping devices. The method may further includeperforming an intraoperative adjustment on the position of the secondtemplate on the second surface of the joint, wherein performing theintraoperative adjustment includes adjusting for at least one of jointflexion, joint extension, joint abduction, and joint rotation. Directingmovement of the surgical instrument using the at least one guide of thesecond template may include making one or more cuts or drill holes, themethod further comprising implanting a joint prosthesis as a function ofthe one or more cuts or drill holes. The first template may include atleast one guide, the method further comprising directing movement of asurgical instrument using the at least one guide of the first template.Directing movement of the surgical instrument using the at least oneguide of the first template may include making one or more cuts or drillholes, the method further comprising implanting a joint prosthesis as afunction of the one or more cuts or drill holes. Directing movement ofthe surgical instrument using the at least one guide of the secondtemplate may include making at least one of a cut, a drill hole, and areaming, the method further comprising implanting a joint prosthesis.

In still further related embodiments of the invention, the first surfaceof the joint may be a femoral surface, and the second surface of thejoint may be a tibial surface. The method may further include obtainingelectronic image data of a joint, determining the at least one of abiomechanical axis and an anatomical axis of the joint based, at leastin part, on the electronic image data, wherein the shape and/or positionof the guide of the second template is based, at least in part, on theat least one of the biomechanical axis and the anatomical axis. Theelectronic image data may be obtained pre-operatively, intraoperatively,optically, an MRI, a CT, and/or a spiral CT. The first template mayinclude a thickness based, at least in part, on at least one of athickness of an implant to be attached to the first surface of the jointand a desired space between two opposing surfaces of the joint.

In accordance with another embodiment of the invention, a method ofjoint arthroplasty includes positioning at least one contact surface ofa first template onto a first surface of a joint. A second template iscross-referenced to the first template to align position of the secondtemplate on a second surface of the joint, the second surface opposingthe first surface. The second template includes at least one guide.Movement of the surgical instrument is directed using the at least oneguide of the second template.

In accordance with another embodiment of the invention, a method ofjoint arthroplasty includes positioning at least one contact surface ofa first template onto a first surface of a joint, wherein the at leastone contact surface of the first template is substantially a mirrorimage of the first surface. A second template is cross-referenced to thefirst template to align position of the second template onto a secondsurface of the joint, the at least one contact surface of the secondtemplate substantially a mirror image of the second surface of thejoint. The second template includes at least one guide. Movement of thesurgical instrument is directed using the at least one guide of thesecond template.

In accordance with another embodiment of the invention, a method ofjoint arthroplasty includes positioning at least one contact surface ofa first template onto a first surface of a joint. A second template iscross-referenced to the first template to align position of the secondtemplate on a second surface of the joint, the second template includingat least one guide. Cross-referencing allows rotation of the secondtemplate relative to one of a biomechanical and an anatomical axis.Movement of the surgical instrument is directed using the at least oneguide of the second template.

In accordance with another embodiment of the invention, a method ofjoint arthroplasty includes obtaining electronic image data of a joint,and determining width space of the joint based, at least in part, on theelectronic image data. A template is provided that includes at least oneguide for directing movement of a surgical instrument, wherein at leastone of the shape and position of the guide is based, at least in part,on the width space of the joint.

In accordance with related embodiment of the invention, the template mayinclude at least one surface for engaging a surface of a joint, thesurface being a mirror image of portions or all of the surface.Obtaining electronic image data may include at least one of a CT scan,MRI scan, optical scan, and a ultrasound imaging. Obtaining electronicimage data may include obtaining image data of a medial space, a lateralspace, anterior space, and/or posterior space of the joint. At least twoof the lateral space, anterior space, and posterior space of the jointmay be compared. Obtaining image data may be performed in two dimensionsor three dimensions. Determining width of the joint may includemeasuring the distance from the subchondral bone plate of one articularsurface to the subchondral bone plate of the opposing articular surface.Alternatively, determining width of the joint may include measuring thedistance from the subchondral bone plate of one articular surface to thesubchondral bone plate of the opposing articular surface. Obtaining theimage data of the joint may be performed in at least one of jointflexion, joint extension, and joint rotation. At least one of the shapeand position of the guide may be further based, at least in part, on theanatomical or biomechanical axis alignment of the joint.

In accordance with another embodiment of the invention, a method ofjoint arthroplasty includes obtaining electronic image data of a joint,and determining cartilage loss associated with the joint based, at leastin part, on the electronic image data. A template may be provided thatincludes at least one guide for directing movement of a surgicalinstrument so as to correct an axis alignment of the joint, wherein atleast one of the shape and position of the guide is based, at least inpart, on the cartilage loss.

In accordance with related embodiments of the invention, the method mayfurther include measuring at least one axis associated with the joint.Measuring may include a standing x-ray, a weight bearing x-ray, a CTscout scan, a MRI localizer scan, a CT scan, and/or a MRI scan.Obtaining image data may include a spiral CT, spiral CT arthography,MRI, optical imaging, optical coherence tomography, and/or ultrasound.The template may include at least one contact surface for engaging asurface of the joint, the contact surface being a mirror image ofportions or all of the joint surface.

In accordance with another embodiment of the invention, a method forjoint arthroplasty includes obtaining electronic image data of a joint,and determining a plurality of measurements based, at least in part, onthe image data. The measurements may be selected from at least one of anaxis associated with the joint and a plane associated with the joint. Atemplate is provided that includes at least one guide for directingmovement of a surgical instrument, wherein at least one of the shape andposition of the guide is based, at least in part, on the plurality ofmeasurements.

In accordance with related embodiments of the invention, obtaining imagedata of the joint may include an x-ray, a standing x-ray, a CT scan, anMRI scan, CT scout scans, and/or MRI localizer scans. The plurality ofmeasurements may include a plurality of axis, a plurality of planes, ora combination of an axis and a plane. The template may include at leastone contact surface for engaging a surface of a joint, the contactsurface being a mirror image of portions or all of the joint surface.

In accordance with another embodiment of the invention, a surgical toolincludes a template having a surface for engaging a joint surface, thesurface being a mirror image of a portion or all of the joint surface.The template further includes two or more guides for directing movementof a surgical instrument, wherein the shape and/or position of at leastone of the guides is based, at least in part, on at least one axisrelated to said joint.

In accordance with related embodiments of the invention, the templatefurther includes a block removably attached to the surface, the blockincluding the two or more guides. The two or more guides may include atleast one guide for a cut, a milling, and a drilling. A second surgicaltool may be attached to the template, the second tool including at leastone guide aperture for guiding a surgical instrument. At least one guideof the second surgical tool may guide a surgical instrument to make cutsthat are parallel, non-parallel, perpendicular, or non-perpendicular tocuts guided by the first template.

In accordance with another embodiment of the invention, a method ofjoint arthroplasty includes performing an extended scan of a joint toobtain electronic image data that includes the joint and at least 15 cmor greater beyond the joint. At least one of an anatomical and abiomechanical axis associated with the joint is determined based, atleast in part, on the electronic image data. A template is provided thatincludes at least one guide for directing movement of a surgicalinstrument, wherein at least one of the shape and position of the guideis based, at least in part, on the at least one of the anatomical andthe biomechanical axis.

In accordance with related embodiments of the invention, the joint maybe a knee joint, and performing the extended scan of a joint to obtainelectronic image data includes obtaining electronic image data at least15 cm, 20 cm, or 25 cm beyond the tibiofemoral joint space.

In accordance with another embodiment of the invention, a method ofjoint arthroplasty includes performing an imaging scan acquisition thatobtains electronic image data through more than one joint. At least oneof an anatomical axis and a biomechanical axis associated with the jointis determined based, at least in part, on the electronic image data. Atemplate is provided that includes at least one guide for directingmovement of a surgical instrument, wherein at least one of the shape andposition of the guide is based, at least in part, on the at least one ofthe anatomical and the biomechanical axis.

In accordance with related embodiments of the invention, performing theimaging acquisition includes performing a CT, MRI, an X-ray, and/or atwo-plane x-ray, wherein the CT and the MRI includes a slice, spiral,and/or volume acquisition. The guide may direct the movement of asurgical instrument to correct a varus deformity and/or a valgusdeformity.

In accordance with another embodiment of the invention, a method ofjoint arthroplasty includes obtaining a first image of a joint in afirst plane, wherein the first image generates a first image volume. Asecond image of a joint in a second plane is obtained, wherein thesecond image generates a second image data volume. The first and secondimage data volumes is combined to form a resultant image data volume,wherein the resultant image data volume is substantially isotropic. Atemplate is provided based on the resultant image data volume, thetemplate including at least one surface for engaging a first surface ofa joint, the surface being a mirror image of portions or all of thefirst surface. The template further includes at least one guide fordirecting movement of a surgical instrument.

In accordance with related embodiments of the invention, obtaining thefirst image and the second image may includes a spiral CT, volumetricCT, and/or an MRI scan.

In accordance with another embodiment of the invention, a method forjoint arthroplasty includes performing a first cut on a joint to createa first cut joint surface. Performing the first cut includes positioningat least one contact surface of a first template onto a first surface ofa joint, the at least one contact surface being a mirror image of thefirst surface of the joint. The first template includes a guide fordirecting movement of a surgical instrument to perform the first cut.The first cut is cross-referenced to perform a second cut associatedwith an opposing surface of the joint.

In accordance with related embodiments of the invention,cross-referencing the first cut to make the second cut may includeattaching a second template to the first template so as to assistpositioning at least one contact surface of the second template onto asecond surface of the joint. The second template includes a guide fordirecting movement of a surgical instrument to perform the second cut.The second template may include at least one contact surface being amirror image of the second surface of the joint. Cross-referencing thefirst cut to make the second cut may include positioning at least onecontact surface of a third template onto at least a portion of the firstcut surface, and attaching a second template to the third template so asto position at least one contact surface of the second template onto asecond surface of the joint. The at least one contact surface of thethird template may be a mirror image of the first cut surface. The firstcut may be a horizontal femoral cut, with the second cut being avertical femoral cut. The first cut may be femoral cut with the secondcut being a tibial cut. The first cut may be a femoral cut, and thesecond cut is a patellar cut. The first cut may be an acetabular reamingand the second cut is a femoral cut.

In accordance with another embodiment of the invention, a method forjoint arthroplasty includes positioning at least one contact surface ofa template onto a surface of a joint, the at least one contact surfacebeing a mirror image of at least a portion of the surface of the joint.The template includes a guide for directing movement of a surgicalinstrument. The first template is stabilized onto the first surface.

In accordance with related embodiments of the invention, the method mayfurther include obtaining electronic image data of the joint, anddetermining a shape of the at least one contact surface of the firsttemplate based, at least in part, on electronic image data. Stabilizingmay include using k-wires, a screw, an anchor, and/or a drill bit leftin place on the joint. Stabilizing may includes positioning the contactsurface on at least one or more concavities and convexities on thejoint. Stabilizing may include positioning the contact surface on atleast one concavity and at least convexity on the joint. Stabilizing mayinclude positioning the contact surface, at least partially, on anarthritic portion of the joint. Stabilizing may include positioning thecontact surface, at least partially, on an interface between a normaland an arthritic portion of the joint. Stabilizing may includepositioning the contact surface, at least partially, against an anatomicfeature. The anatomic feature may be a trochlea, an intercondylar notch,a medial condyle and a lateral condyle, a medial trochlea and a lateraltrochlea, a medial tibial plateau and a lateral tibial plateau, a foveacapities, an acetabular fossa, a tri-radiate cartilage, an acetabularwall, or an acetabular rim. Positioning the contact surface on thesurface of the joint may include positioning the contact surface on, atleast partially, a normal portion of the joint. Determining the positionof the guide on the template may be based, at least in part, on ligamentbalancing and/or to optimize at least one of flexion and extension gap.The method may further include adjusting the position of the guiderelative to the joint intraoperatively, using for example, a spacer, aratchet device, and a pin that allows rotation.

In accordance with another embodiment of the invention, a method forjoint arthroplasty includes positioning at least one contact surface ofa template onto a surface of a joint, such that the contact surface, atleast partially, rests on, and is a mirror image of, an interfacebetween an arthritic and a normal portion of the joint surface. Thetemplate includes a guide for directing movement of a surgicalinstrument. A surgical intervention is made on the joint with thesurgical instrument based, at least in part, on the guide.

In accordance with another embodiment of the invention, a templateincludes at least one contact surface for positioning onto a surface ofa joint, the contact surface at least partially being a mirror image ofan interface between an arthritic and a normal portion of the jointsurface. A guide directs movement of a surgical instrument.

In accordance with another embodiment of the invention, a method forjoint arthroplasty includes positioning at least one contact surface ofa template onto a surface of a joint, such that the contact surface, atleast partially, rests on, and is a mirror image of, an arthriticportion of the joint surface. The template includes a guide fordirecting movement of a surgical instrument. A surgical intervention ismade on the joint with the surgical instrument based, at least in part,on the guide.

In accordance with another embodiment of the invention, a templateincludes at least one contact surface for positioning onto a surface ofa joint, the contact surface at least partially being a mirror image ofa normal portion of the joint surface. The template includes a guide fordirecting movement of a surgical instrument.

In accordance with another embodiment of the invention, a method forjoint arthroplasty includes performing a phantom scan of one of a MRIand CT instrument. Using the one of the an MRI and CT instrument, a scanon a joint is performed. A shape of the at least one contact surface ofthe first template is determined, based, at least in part, on thephantom scan and the scan of the joint, the at least one contact surfacebeing a mirror image of at least a portion of the surface of the joint.The template includes a guide for directing movement of a surgicalinstrument.

In accordance with related embodiments of the invention, the phantomscan may be performed prior to the scan of the joint, the method furthercomprising adjusting the one of the MRI and the CT instrument. Thephantom scan may be performed after performing the scan of the joint,wherein the scan of the joint is optimized based on the phantom scan.

In accordance with another embodiment of the invention, a method forjoint arthroplasty includes determining a desired femoral componentrotation for one of a uni-compartmental or total knee replacement. Atemplate is provided that includes at least one guide for directingmovement of a surgical instrument, attached linkage, and/or tool. Atleast one of the shape and position of the guide is based, at least inpart, on the desired femoral component rotation.

In accordance with related embodiments of the invention, determining thedesired femoral component rotation may include measuring one or moreanatomic axis and/or planes relevant to femoral component rotation. Theone or more anatomic axis and/or planes may be a transepicondylar axis,the Whiteside line, and/or the posterior condylar axis. The guide maydirect a femoral cut, the method further comprising rotating thetemplate so that the femoral cut is parallel to a tibial cut withsubstantially equal tension medially and laterally applied from medialand lateral ligaments and soft tissue.

In accordance with another embodiment of the invention, a method forjoint arthroplasty includes determining a desired tibial componentrotation for one of a uni-compartmental or total knee replacement. Atibial template is provided that includes at least one guide fordirecting movement of a surgical instrument, attached linkage, and/ortool. At least one of the shape and position of the guide is based, atleast in part, on the desired tibial component rotation.

In accordance with related embodiments of the invention, determining thedesired tibial component rotation may include measuring one or moreanatomic axis and/or planes relevant to tibial component rotation. Theone or more anatomic axis and/or planes may be at an anteroposterioraxis of the tibia, and/or the meidal one-third of the tibial tuberosity.The guide may direct a femoral cut, the method further comprisingrotating the template so that the femoral cut is parallel to a tibialcut with substantially equal tension medially and laterally applied frommedial and lateral ligaments and soft tissue.

In accordance with another embodiment of the invention, a method of hiparthroplasty includes determining leg length discrepancy and obtainingelectronic image data of the hip joint. A template is provided thatincludes at least one guide for directing movement of a surgicalinstrument, attached linkage, and/or tool. The template includes atleast one contact surface that is a mirror image of the femoral neck,wherein at least one of the shape and position of the template and/orguide is based, at least in part, on the electronic image data.

In accordance with related embodiments of the invention, determining leglength discrepancy may include a standing x-ray of the leg, a CT scoutscan, a CT, and/or an MRI. The guide may assist a surgical instrument incutting the femoral neck.

In accordance with another embodiment of the invention, a method forjoint arthroplasty includes determining a desired femoral componentrotation for a hip. A template is provided that includes at least oneguide for directing movement of a surgical instrument, attached linkage,and/or tool. At least one of the shape and position of the guide isbased, at least in part, on the desired femoral component rotation.

In accordance with another embodiment of the invention, a method forjoint arthroplasty includes determining a desired acetabular componentrotation for a hip. An acetabular template is provided that includes atleast one guide for directing movement of a surgical instrument,attached linkage, and/or tool. At least one of the shape and position ofthe guide is based, at least in part, on the desired acetabularcomponent rotation.

In accordance with another embodiment of the invention, a method forjoint arthroplasty includes determining a desired humerus componentrotation for a shoulder. A template is provided that includes at leastone guide for directing movement of a surgical instrument, attachedlinkage, and/or a tool. At least one of the shape and position of theguide is based, at least in part, on the desired humerus componentrotation.

In accordance with another embodiment of the invention, a method forjoint arthroplasty includes providing a template that includes at leastone surface for engaging a surface of a joint based, at least in part,on substantially isotropic input data. The surface is a mirror image ofportions or all of the joint surface. The template includes at least oneguide for directing movement of a surgical instrument.

In related embodiments of the invention, said input data is acquiredusing fusion of image planes, or substantially isotropic MRI and spiralCT.

In accordance with another embodiment of the invention, a method forligament repair includes obtaining electronic image data of at least onesurface associated with a ligament. A first template is created based,at least in part, on the image data. The first template has at least onecontact surface that conforms with at least a portion of the surface.The first template includes at least one guide for directing movement ofa surgical instrument involved with the ligament repair.

In related embodiments of the invention, the ligament may be an anteriorcruciate ligament or a posterior cruciate ligament. The method mayfurther include determining a tunnel site for a ligament graft.Determining the tunnel site may include identifying an origin of theligament on a first articular surface, and an insertion position onto asecond articular surface opposing the first articular surface.Determining the tunnel site may include identifying at least one of abony landmark and a remainder of a ligament based on the image data. Thesurface may be adjacent to the tunnel site, or a non-weight bearingsurface. The first template may includes a drill guide aperture, themethod further including positioning the template such that the at leastone contact surface contacts the at least a portion of the surface, anddrilling a ligament tunnel, wherein the drilling is guided by the drillguide aperture. At least one of the shape, position and orientation ofthe drill guide aperture on the first template may be based, at least inpart, on a distance of the tunnel to adjacent cortical bone. The drillguide aperture may includes a stop, such that a desired drill depth isobtained. The image data may be obtained preoperatively. The image datamay be obtained by a CT scan or an MRI scan. The image data may beobtained in joint flexion, joint extension, joint abduction, jointadduction, and/or joint rotation. The method may further includeidentifying a graft harvest site based on the image data, and using thefirst template to guide harvesting of at least one of ligament and boneform the graft harvest site. The method may further includecross-referencing a second template to the first template to alignposition of the second template on a second surface associated with theligament, the second template including at least one guide, anddirecting movement of the instrument using the at least one guide of thesecond template relative to said guide. The first and second surfacesmay be opposing articular surfaces. The first surface may be a femoralsurface and the second surface may be a tibial surface. The firsttemplate may include a tissue retractor. The tissue retractor may be aflange or an extender on the template. The template may be used forsingle bundle or a double bundle ligament reconstruction.

In any of the embodiments and aspects described herein, the joint canbe, without limitation, a knee, shoulder, hip, vertebrae, elbow, ankle,foot, toe, hand, wrist or finger.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing features of the invention will be more readily understoodby reference to the following detailed description, taken with referenceto the accompanying drawings, in which:

FIG. 1 is a flowchart depicting various methods of the present inventionincluding, measuring the size of an area of diseased cartilage orcartilage loss, measuring the thickness of the adjacent cartilage, andmeasuring the curvature of the articular surface and/or subchondralbone. Based on this information, a best-fitting implant can be selectedfrom a library of implants or a patient specific custom implant can begenerated. The implantation site is subsequently prepared and theimplantation is performed.

FIG. 2 is a reproduction of a three-dimensional thickness map of thearticular cartilage of the distal femur. Three-dimensional thicknessmaps can be generated, for example, from ultrasound, CT or MRI data.Dark holes within the substances of the cartilage indicate areas of fullthickness cartilage loss.

FIG. 3A shows an example of a Placido disc of concentrically arrangedcircles of light. FIG. 3B shows an example of a projected Placido discon a surface of fixed curvature.

FIG. 4 shows a reflection resulting from a projection of concentriccircles of light (Placido Disk) on each femoral condyle, demonstratingthe effect of variation in surface contour on the reflected circles.

FIG. 5 shows an example of a 2D topographical map of an irregularlycurved surface.

FIG. 6 shows an example of a 3D topographical map of an irregularlycurved surface.

FIGS. 7A-H illustrate, in cross-section, various stages of kneeresurfacing, in accordance with various embodiments of the invention.

FIG. 7A shows an example of normal thickness cartilage and a cartilagedefect. FIG. 7B shows an imaging technique or a mechanical, optical,laser or ultrasound device measuring the thickness and detecting asudden change in thickness indicating the margins of a cartilage defect.FIG. 7C shows a weight-bearing surface mapped onto the articularcartilage. FIG. 7D shows an intended implantation site and cartilagedefect. FIG. 7E depicts placement of an exemplary single componentarticular surface repair system. FIG. 7F shows an exemplarymulti-component articular surface repair system. FIG. 7G shows anexemplary single component articular surface repair system. FIG. 7Hshows an exemplary multi-component articular surface repair system.

FIGS. 8A-E, illustrate, in cross-section, exemplary knee imaging andresurfacing, in accordance with various embodiments of the invention.FIG. 8A shows a magnified view of an area of diseased cartilage. FIG. 8Bshows a measurement of cartilage thickness adjacent to the defect. FIG.8C depicts placement of a multi-component mini-prosthesis for articularresurfacing. FIG. 8D is a schematic depicting placement of a singlecomponent mini-prosthesis utilizing stems or pegs. FIG. 8E depictsplacement of a single component mini-prosthesis utilizing stems and anopening for injection of bone cement.

FIGS. 9A-C, illustrate, in cross-section, other exemplary kneeresurfacing devices and methods, in accordance with various embodimentsof the invention. FIG. 9A depicts normal thickness cartilage in theanterior and central and posterior portion of a femoral condyle and alarge area of diseased cartilage in the posterior portion of the femoralcondyle. FIG. 9B depicts placement of a single component articularsurface repair system. FIG. 9C depicts a multi-component articularsurface repair system.

FIGS. 10A-B are flow charts illustrating steps for forming a device insitu, in accordance with various embodiments of the invention.

FIGS. 11A-G illustrate, in cross-section, the use of an inflation deviceto form an implant, in accordance with various embodiments of theinvention. FIG. 11A illustrates a single lumen balloon inserted betweentwo joint surfaces where the inflation occurs within the bounds of thejoint. FIG. 11B illustrates another single lumen balloon insertedbetween two joint surfaces where the inflatable surfaces extend beyond afirst and second edge of a joint. FIG. 11C illustrates another singlelumen balloon between two joint surfaces. FIG. 11D illustrates amulti-balloon solution using two balloons where the balloons areadjacent to each other within the joint. FIG. 11E illustrates analternative multi-balloon solution wherein a first balloon is comprisedwithin a second balloon. FIG. 11F illustrates another multi-balloonsolution where a first balloon lies within the lumen of a second balloonand further wherein the second balloon is adjacent a third balloon. FIG.11G illustrates a 3 balloon configuration wherein a first balloon liesadjacent a second balloon and a third balloon fits within the lumen ofone of the first or second balloon.

FIGS. 12A-E illustrate a variety of cross-sectional shapes achievedusing balloons with variable wall thicknesses or material compositions,in accordance with various embodiments of the invention. In FIG. 12A theinflation device enables the implant to achieve a surface conforming tothe irregularities of the joint surface. In FIG. 12B the inflationdevice enables the implant to achieve a surface that sits above theirregular joint surface; FIG. 12C illustrates a device formed where acentral portion of the device sits above the joint surfaceirregularities while the proximal and distal ends illustrated form alateral abutting surface to the joint defects. FIG. 12D illustrates adevice formed using a first inflation device within a second inflationdevice, with an exterior configuration similar to that shown in FIG.12A; while FIG. 12E illustrates an alternative device formed using atleast two different inflation devices having an exterior shape similarto the device shown in FIG. 12C.

FIGS. 13A-J(1-3) show a variety of cross-sectional views of theinflation devices shown in FIGS. 11 and 12 taken at a positionperpendicular to the views shown in FIGS. 11 and 12.

FIGS. 14A-J illustrate the use of a retaining device to form an implantin situ, in accordance with various embodiments of the invention.

FIGS. 15A-B show single and multiple component devices, in accordancewith various embodiments of the invention. FIG. 15A shows an exemplarysingle component articular surface repair system with varying curvatureand radii. FIG. 15B depicts a multi-component articular surface repairsystem with a second component that mirrors the shape of the subchondralbone and a first component closely matches the shape and curvature ofthe surrounding normal cartilage.

FIGS. 16A-B show exemplary articular repair systems having an outercontour matching the surrounding normal cartilage, in accordance withvarious embodiments of the invention. The systems are implanted into theunderlying bone using one or more pegs.

FIG. 17 shows a perspective view of an exemplary articular repair deviceincluding a flat surface to control depth and prevent toggle; anexterior surface having the contour of normal cartilage; flanges toprevent rotation and control toggle; a groove to facilitate tissuein-growth, in accordance with one embodiment of the invention.

FIGS. 18A-D depict, in cross-section, another example of an implant withmultiple anchoring pegs, in accordance with various embodiments of theinvention. FIG. 18B-D show various cross-sectional representations ofthe pegs: FIG. 18B shows a peg having a groove; FIG. 18C shows a pegwith radially-extending arms that help anchor the device in theunderlying bone; and FIG. 18D shows a peg with multiple grooves orflanges.

FIG. 19A-B depict an overhead view of an exemplary implant with multipleanchoring pegs and depict how the pegs are not necessarily linearlyaligned along the longitudinal axis of the device, in accordance withvarious embodiments of the invention.

FIGS. 20A-E depict an exemplary implant having radially extending arms,in accordance with various embodiments of the invention. FIGS. 20B-E areoverhead views of the implant showing that the shape of the peg need notbe conical.

FIG. 21A illustrates a femur, tibia and fibula along with the mechanicaland anatomic axes. FIGS. 21B-E illustrate the tibia with the anatomicand mechanical axis used to create a cutting plane along with a cutfemur and tibia. FIG. 21F illustrates the proximal end of the femurincluding the head of the femur.

FIG. 22 shows an example of a surgical tool having one surface matchingthe geometry of an articular surface of the joint, in accordance withone embodiment of the invention. Also shown is an aperture in the toolcapable of controlling drill depth and width of the hole and allowingimplantation of an insertion of implant having a press-fit design.

FIG. 23 is a flow chart depicting various methods of the invention usedto create a mold for preparing a patient's joint for arthroscopicsurgery, in accordance with one embodiment of the invention.

FIG. 24A depicts, in cross-section, an example of a surgical toolcontaining an aperture through which a surgical drill or saw can fit, inaccordance with one embodiment of the invention. The aperture guides thedrill or saw to make the proper hole or cut in the underlying bone.Dotted lines represent where the cut corresponding to the aperture willbe made in bone. FIG. 24B depicts, in cross-section, an example of asurgical tool containing apertures through which a surgical drill or sawcan fit and which guide the drill or saw to make cuts or holes in thebone, in accordance with one embodiment of the invention. Dotted linesrepresent where the cuts corresponding to the apertures will be made inbone.

FIGS. 25A-R illustrate tibial cutting blocks and molds used to create asurface perpendicular to the anatomic axis for receiving the tibialportion of a knee implant, in accordance with various embodiments of theinvention.

FIGS. 26A-O illustrate femur cutting blocks and molds used to create asurface for receiving the femoral portion of a knee implant, inaccordance with various embodiments of the invention. FIG. 26Pillustrates an axis defined by the center of the tibial plateau and thecenter of the distal tibia. FIG. 26q shows an axis defining the centerof the tibial plateau to the femoral head. FIGS. 26R and 26S showisometric views of a femoral template and a tibial template,respectively, in accordance with various embodiments of the invention.FIG. 26T illustrates a femoral guide reference tool attached to thefemoral template, in accordance with an embodiment of the invention.FIG. 26U illustrates a sample implant template positioned on thechondyle, in accordance with an embodiment of the invention. FIG. 26V isan isometric view of the interior surface of the sample implanttemplate, in accordance with an embodiment of the invention. FIG. 26W isan isometric view of the tibial template attached to the sample implant,in accordance with an embodiment of the invention. FIG. 26X shows atibial template that may be used, after the tibial cut has been made, tofurther guide surgical tools, in accordance with an embodiment of theinvention. FIG. 26Y shows a tibial implant 2415 and femoral implantinserted onto the tibia and femur, respectively, after theabove-described cuts have been made, in accordance with an embodiment ofthe invention. FIG. 26Y shows a tibial implant and femoral implantinserted onto the tibia and femur, respectively, in accordance with anembodiment of the invention.

FIG. 27A-G illustrate patellar cutting blocks and molds used to preparethe patella for receiving a portion of a knee implant, in accordancewith various embodiments of the invention.

FIG. 28A-H illustrate femoral head cutting blocks and molds used tocreate a surface for receiving the femoral portion of a knee implant, inaccordance with various embodiments of the invention.

FIG. 29A-D illustrate acetabulum cutting blocks and molds used to createa surface for a hip implant, in accordance with various embodiments ofthe invention.

FIG. 30 illustrates a 3D guidance template in a hip joint, wherein thesurface of the template facing the joint is a mirror image of a portionof the joint that is not affected by the arthritic process, inaccordance with one embodiment of the invention.

FIG. 31 illustrates a 3D guidance template for an acetabulum, whereinthe surface of the template facing the joint is a mirror image of aportion of the joint that is affected by the arthritic process, inaccordance with an embodiment of the invention.

FIG. 32 illustrates a 3D guidance template designed to guide a posteriorcut using a posterior reference plane, in accordance with an embodimentof the invention. The joint facing surface of the template is, at leastin part, a mirror image of portions of the joint that are not altered bythe arthritic process.

FIG. 33 illustrates a 3D guidance template designed to guide an anteriorcut using an anterior reference plane, in accordance with an embodimentof the invention. The joint facing surface of the template is, at leastin part, a mirror image of portions of the joint that are altered by thearthritic process.

FIG. 34 illustrates a 3D guidance template for guiding a tibial cut (notshown), wherein the tibia includes an arthritic portion, in accordancewith an embodiment of the invention. The template is designed to avoidthe arthritic process by spanning across a defect or cyst.

FIG. 35 illustrates a 3D guidance template for guiding a tibial cut, inaccordance with an embodiment of the invention. The interface betweennormal and arthritic tissue is included in the shape of the template.

FIG. 36A illustrates a 3D guidance template wherein the surface of thetemplate facing the joint is a mirror image of at least portions of thesurface of a joint that is healthy or substantially unaffected by thearthritic process, in accordance with an embodiment of the invention.FIG. 36B illustrates the 3D guidance template wherein the surface of thetemplate facing the joint is a mirror image of at least portions of thesurface of the joint that is healthy or substantially unaffected by thearthritic process, in accordance with an embodiment of the invention.The diseased area is covered by the template, but the mold is notsubstantially in contact with it. FIG. 36C illustrates the 3D guidancetemplate wherein the surface of the template facing the joint is amirror image of at least portions of the surface of the joint that arearthritic, in accordance with an embodiment of the invention. FIG. 36Dillustrates the 3D guidance template wherein the template closelymirrors the shape of the interface between substantially normal or nearnormal and diseased joint tissue, in accordance with an embodiment ofthe invention.

FIGS. 37A-D show multiple molds with linkages on the same articularsurface (A-C) and to an opposing articular surface (D), in accordancewith various embodiments of the invention.

FIG. 38 illustrates a deviation in the AP plane of the femoral andtibial axes in a patient, in accordance with an embodiment of theinvention.

FIG. 39 is a flow diagram showing a method wherein measured leg lengthdiscrepancy is utilized to determine the optimal cut height of a femoralneck cut for total hip arthroplasty, in accordance with an embodiment ofthe invention.

FIGS. 40A-C illustrate the use of 3D guidance templates for performingligament repair, in accordance with an embodiment of the invention.

FIG. 41 shows an example of treatment of CAM impingement using a 3Dguidance template, in accordance with an embodiment of the invention.

FIG. 42 shows an example of treatment of Pincer impingement using a 3Dguidance template, in accordance with an embodiment of the invention.

FIG. 43 shows an example of an intended site for placement of a femoralneck mold for total hip arthroplasty, in accordance with one embodimentof the invention.

FIG. 44 shows an example of a femoral neck mold with handle and slot, inaccordance with an embodiment of the invention.

FIG. 45 shows an example of a posterior acetabular approach for totalhip replacement, in accordance with an embodiment of the invention.

FIG. 46 shows an example of a guidance mold used for reaming the sitefor an acetabular cup, in accordance with an embodiment of theinvention.

FIG. 47 shows an example of an optional second femoral neck mold, placedon the femoral neck cut, providing and estimate of anteversion andlongitudinal femoral axis.

FIG. 48A illustrates a patella modeled from CT data. FIGS. 48B-Dillustrate a mold guide, and then the mold guide placed on an articularsurface of the patella. FIG. 48E illustrates a drill placed into apatella through mold drill guide. FIG. 48F illustrates a reamer used toprepare the patella.

FIG. 49A illustrates a reamer made for each patella size. FIG. 49Billustrates a reamed patella ready for patella implantation.

FIGS. 50A-F illustrate a recessed patella implanted on a patella.

DETAILED DESCRIPTION OF THE INVENTION

The following description is presented to enable any person skilled inthe art to make and use the invention. Various modifications to theembodiments described will be readily apparent to those skilled in theart, and the generic principles defined herein can be applied to otherembodiments and applications without departing from the spirit and scopeof the present invention as defined by the appended claims. Thus, thepresent invention is not intended to be limited to the embodimentsshown, but is to be accorded the widest scope consistent with theprinciples and features disclosed herein. To the extent necessary toachieve a complete understanding of the invention disclosed, thespecification and drawings of all issued patents, patent publications,and patent applications cited in this application are incorporatedherein by reference.

3D guidance surgical tools, referred to herein as a 3D guidance surgicaltemplates, that may be used for surgical assistance may include, withoutlimitation, using templates, jigs and/or molds, including 3D guidancemolds. It is to be understood that the terms “template,” “jig,” “mold,”“3D guidance mold,” and “3D guidance template,” shall be usedinterchangeably within the detailed description and appended claims todescribe the tool unless the context indicates otherwise.

3D guidance surgical tools that may be used may include guide apertures.It is to be understood that the term guide aperture shall be usedinterchangeably within the detailed description and appended claims todescribe both guide surface and guide elements.

As will be appreciated by those of skill in the art, the practice of thepresent invention employs, unless otherwise indicated, conventionalmethods of x-ray imaging and processing, x-ray tomosynthesis, ultrasoundincluding A-scan, B-scan and C-scan, computed tomography (CT scan),magnetic resonance imaging (MRI), optical coherence tomography, singlephoton emission tomography (SPECT) and positron emission tomography(PET) within the skill of the art. Such techniques are explained fullyin the literature and need not be described herein. See, e.g., X-RayStructure Determination: A Practical Guide, 2nd Edition, editors Stoutand Jensen, 1989, John Wiley & Sons, publisher; Body Conn.: A PracticalApproach, editor Slone, 1999, McGraw-Hill publisher; X-ray Diagnosis: APhysician's Approach, editor Lam, 1998 Springer-Verlag, publisher; andDental Radiology: Understanding the X-Ray Image, editor LaetitiaBrocklebank 1997, Oxford University Press publisher. See also, TheEssential Physics of Medical Imaging (2^(nd) Ed.), Jerrold T. Bushberg,et al.

The present invention provides methods and compositions for repairingjoints, particularly for repairing articular cartilage and forfacilitating the integration of a wide variety of cartilage repairmaterials into a subject. Among other things, the techniques describedherein allow for the customization of cartilage repair material to suita particular subject, for example in terms of size, cartilage thicknessand/or curvature. When the shape (e.g., size, thickness and/orcurvature) of the articular cartilage surface is an exact or nearanatomic fit with the non-damaged cartilage or with the subject'soriginal cartilage, the success of repair is enhanced. The repairmaterial can be shaped prior to implantation and such shaping can bebased, for example, on electronic images that provide informationregarding curvature or thickness of any “normal” cartilage surroundingthe defect and/or on curvature of the bone underlying the defect. Thus,the current invention provides, among other things, for minimallyinvasive methods for partial joint replacement. The methods will requireonly minimal or, in some instances, no loss in bone stock. Additionally,unlike with current techniques, the methods described herein will helpto restore the integrity of the articular surface by achieving an exactor near anatomic match between the implant and the surrounding oradjacent cartilage and/or subchondral bone.

Advantages of the present invention can include, but are not limited to,(i) customization of joint repair, thereby enhancing the efficacy andcomfort level for the patient following the repair procedure; (ii)eliminating the need for a surgeon to measure the defect to be repairedintraoperatively in some embodiments; (iii) eliminating the need for asurgeon to shape the material during the implantation procedure; (iv)providing methods of evaluating curvature of the repair material basedon bone or tissue images or based on intraoperative probing techniques;(v) providing methods of repairing joints with only minimal or, in someinstances, no loss in bone stock; and (vi) improving postoperative jointcongruity.

Thus, the methods described herein allow for the design and use of jointrepair material that more precisely fits the defect (e.g., site ofimplantation) and, accordingly, provides improved repair of the joint.

I. Assessment of Joints and Alignment

The methods and compositions described herein can be used to treatdefects resulting from disease of the cartilage (e.g., osteoarthritis),bone damage, cartilage damage, trauma, and/or degeneration due tooveruse or age. The invention allows, among other things, a healthpractitioner to evaluate and treat such defects. The size, volume andshape of the area of interest can include only the region of cartilagethat has the defect, but preferably will also include contiguous partsof the cartilage surrounding the cartilage defect.

As will be appreciated by those of skill in the art, size, curvatureand/or thickness measurements can be obtained using any suitabletechnique. For example, one-dimensional, two-dimensional, and/orthree-dimensional measurements can be obtained using suitable mechanicalmeans, laser devices, electromagnetic or optical tracking systems,molds, materials applied to the articular surface that harden and“memorize the surface contour,” and/or one or more imaging techniquesknown in the art. Measurements can be obtained non-invasively and/orintraoperatively (e.g., using a probe or other surgical device). As willbe appreciated by those of skill in the art, the thickness of the repairdevice can vary at any given point depending upon the depth of thedamage to the cartilage and/or bone to be corrected at any particularlocation on an articular surface.

As illustrated in FIG. 1, typically the process begins by firstmeasuring the size of the area of diseased cartilage or cartilage loss10. Thereafter the user can optionally measure the thickness of adjacentcartilage 20. Once these steps are performed, the curvature of thearticular surface is measured 30. Alternatively, the curvature ofsubchondral bone can be measured.

Once the size of the defect is known, either an implant can be selectedfrom a library 32 or an implant can be generated based on the patientspecific parameters obtained in the measurements and evaluation 34.Prior to installing the implant in the joint, the implantation site isprepared 40 and then the implant is installed 42. One or more of thesesteps can be repeated as necessary or desired as shown by the optionalrepeat steps 11, 21, 31, 33, 35, and 41.

A. Imaging Techniques

i. Thickness and Curvature

As will be appreciated by those of skill in the art, imaging techniquessuitable for measuring thickness and/or curvature (e.g., of cartilageand/or bone) or size of areas of diseased cartilage or cartilage lossinclude the use of x-rays, magnetic resonance imaging (MRI), computedtomography scanning (CT, also known as computerized axial tomography orCAT), optical coherence tomography, ultrasound imaging techniques, andoptical imaging techniques. (See, also, International Patent PublicationWO 02/22014 to Alexander, et al., published Mar. 21, 2002; U.S. Pat. No.6,373,250 to Tsoref et al., issued Apr. 16, 2002; and Vandeberg et al.(2002) Radiology 222:430-436). Contrast or other enhancing agents can beemployed using any route of administration, e.g. intravenous,intra-articular, etc.

Based on the imaging performed, the software may evaluate the fit ofdifferent implants and/or surgical guide templates with regard todimensions, overall size and shape. The dimensions, overall size andshape may be optimized with regard to cortical bone shape anddimensions, cortical bone thickness, endosteal bone shape, size ofmarrow cavity, articular surface shape and dimensions, subchondral boneshape and dimensions, or subchondral bone thickness. Thus, for example,an implant may either be custom made or selected from a number ofpre-manufactured implants that is optimized with regard to any of thefollowing or combinations thereof: AP dimensions and shape, mediolateraldimensions and shape, superoinferior dimensions and shape, shape of thearticulating surface, shape and dimensions of the interface in contactwith cortical bone, shape and dimensions of intramedullary portions orcomponents. These parameters may also be optimized for implant function,e.g. for different degrees of joint flexion or extension or abduction oradduction or internal or external rotation.

In certain embodiments, CT or MRI is used to assess tissue, bone,cartilage and any defects therein, for example cartilage lesions orareas of diseased cartilage, to obtain information on subchondral boneor cartilage degeneration and to provide morphologic or biochemical orbiomechanical information about the area of damage. Specifically,changes such as fissuring, partial or full thickness cartilage loss, andsignal changes within residual cartilage can be detected using one ormore of these methods. For discussions of the basic NMR principles andtechniques, see MRI Basic Principles and Applications, Second Edition,Mark A. Brown and Richard C. Semelka, Wiley-Liss, Inc. (1999). For adiscussion of MRI including conventional T1 and T2-weighted spin-echoimaging, gradient recalled echo (GRE) imaging, magnetization transfercontrast (MTC) imaging, fast spin-echo (FSE) imaging, contrast enhancedimaging, rapid acquisition relaxation enhancement (RARE) imaging,gradient echo acquisition in the steady state (GRASS), and drivenequilibrium Fourier transform (DEFT) imaging, to obtain information oncartilage, see Alexander, et al., WO 02/22014. Other techniques includesteady state free precision, flexible equilibrium MRI and DESS. Thus, inpreferred embodiments, the measurements produced are based onthree-dimensional images of the joint obtained as described inAlexander, et al., WO 02/22014 or sets of two-dimensional imagesultimately yielding 3D information. Two-dimensional, andthree-dimensional images, or maps, of the cartilage alone or incombination with a movement pattern of the joint, e.g.flexion-extension, translation and/or rotation, can be obtained.Three-dimensional images can include information on movement patterns,contact points, contact zone of two or more opposing articular surfaces,and movement of the contact point or zone during joint motion. Two- andthree-dimensional images can include information on biochemicalcomposition of the articular cartilage. In addition, imaging techniquescan be compared over time, for example to provide up-to-date informationon the shape and type of repair material needed.

Traditional CT and MRI scans utilize two dimensional cross-sectionalimages acquired in different imaging planes to visualize complexthree-dimensional articular anatomy. With computed tomography, theseslices are typically acquired in the axial plane. The in-planeresolution is typically on the order of 0.25×0.25 millimeters. The slicethickness may vary from one to five millimeters. Thus, the resolutionobtained with these imaging studies is not isotropic. Moreover, the CTslices and, similarly with MRI, may be separated by one or moremillimeters. This means that the resolution of the images is excellentwithin the imaging plane. However, two to ten-fold loss in imageresolution can be encountered in a plane perpendicular to the slicesacquired by the CT or MRI scanner. This limitation in resolutionperpendicular to the imaging plane can result in inaccuracies inderiving the three-dimensional shape of, without limitation, an implantand/or a 3-D guidance template, described in more detail below.

In accordance with one embodiment of the invention, spiral CT imaging isutilized to acquire the images rather than standard CT technology. Withrecent CT technology, slip ring technology is incorporated in thescanner. A slip ring is a circular contact with sliding brushes thatallows the gantry to rotate continuously, untethered by electricalwires. The use of slip ring technology eliminates the initiallimitations at the end of each slice acquisition. Thus, the rotatinggantry is free to rotate continuously throughout the examination of ajoint. A slip ring CT scanner design allows greater rotationalvelocities, thereby shortening scan times. With a spiral CT scan data isacquired while the table is moving. As a result, the x-ray source movesin a spiral or helical rather than a circular pattern around thepatient. The speed of the table motion relative to the rotation of theCT gantry is a very important consideration for image quality in helicalor spiral CT scanning. This parameter is call pitch. In a preferredembodiment, spiral CT scans will be acquired through the joint whereinthese spiral CT scans afford a resolution that is isotropic, for example1 millimeter by 1 millimeter by 1 millimeter in x, y and z direction,or, more preferred, 0.75×0.75×0.75 millimeters in x, y and z direction,or, more preferred, 0.5×0.5×0.5 millimeters in x, y and z direction, or,more preferred 0.25×0.25×0.25 millimeters in x, y and z direction. Nearisotropic data sets are also acceptable particularly if the maximumresolution in any one of the three special orientations does not exceed1.5 millimeters, or, more preferred 1.0 millimeters, or, more preferred0.75 millimeters, or, more preferred 0.5 millimeters. Thus, the presentinvention recognizes that the accuracy in placing a 3-D guidancetemplate on an articular surface, or shaping an implant, can be greatlyimproved with isotropic or near isotropic data sets as compared totraditional 2-D slice based data sets derived from either CT or MRI orother imaging technologies. For example, a knee joint scan data acquiredwith near isotropic resolution of 0.4×0.4×0.7 millimeters (e.g. aresolution ratio of less than 2:1 between the different dimensions andresolution in all three dimensions preferably better than 1 mm) willyield greater positional accuracy in placing a 3-D guidance template onthe articular surface than scan data acquired using traditional CTscans, for example, with a scan resolution of 0.4×0.4×1.2 millimeters.

With MRI, standard acquisition call sequences also result in twodimensional slices for displaying complex three dimensional articularanatomy. The two dimensional slices can be acquired using 2-D or 3-DFourier transformation. After the 2-D or 3-D transform, 2-D slices areavailable for image viewing and image processing. Of note, typically theimage resolution in the imaging plane will be two or more fold greaterthan the image resolution perpendicular to the primary imaging plane.Similar to CT, this limitation in spatial resolution in the planeperpendicular to the imaging plane can result in inaccuracies inderiving and subsequently placing 3-D guidance molds. In a preferredembodiment, MRI data is acquired or processed so that the data used forgenerating the 3-D guidance mold or implant has isotropic or nearisotropic resolution. For example, isotropic or near isotropicresolution may be achieved by fusing two non-parallel imaging planesacquired using standard 2-D or 3-D Fourier transform images, registeringthem relative to each other and performing an image fusion (see U.S.patent application Ser. No. 10/728,731, entitled “FUSION OF MULTIPLEIMAGING PLANES FOR ISOTROPIC IMAGING IN MRI AND QUANTITATIVE IMAGEANALYSIS USING ISOTROPIC OR NEAR-ISOTROPIC IMAGING,” hereby incorporatedby reference in its entirety). Alternatively, using latest generationscan technology, for example, with 3-D FSE, 3-D DESS, 3-D MENSA, 3-DPAVA, 3-D LAVA, 3-D MERGE, 3-D MEDIC imaging sequences, multi-channelcoils, high field magnets, advanced gradient technology, isotropic ornear isotropic acquisition using 3-D Fourier transform can be obtained.Using such advanced imaging technology, image resolution of 0.5 by 0.5by 0.8 millimeters or greater may be obtained, achieving near isotropicand even isotropic resolution, with preferably resolution in all threedimensions of less than 1 mm.

As will be appreciated by those of skill in the art, imaging techniquescan be combined, if desired. For example, C-arm imaging or x-rayfluoroscopy can be used for motion imaging, while MRI can yield highresolution cartilage information. C-arm imaging can be combined withintra-articular contrast to visualize the cartilage.

Any of the imaging devices described herein can also be usedintra-operatively (see, also below), for example using a hand-heldultrasound and/or optical probe to image the articular surfaceintra-operatively. FIG. 2 illustrates a reproduction of athree-dimensional thickness map of the articular surface on the distalfemur. The dark holes within the cartilage indicate areas of fullcartilage loss.

ii. Anatomical and Mechanical Axes, Virtual Ligament Balancing

Imaging can be used to determine the anatomical and biomechanical axesof an extremity associated with a joint, which can then be used increating an implant or surgical guide template or mold. Suitable testsinclude, for example, an x-ray, or an x-ray combined with an MRI.Typically, anatomical landmarks are identified on the imaging testresults (e.g., the x-ray film) and those landmarks are then utilized todirectly or indirectly determine the desired axes. Thus, for example, ifsurgery is contemplated in a hip joint, knee joint, or ankle joint, anx-ray can be obtained. This x-ray can be a weight-bearing film of theextremity, for example, a full-length leg film taken while the patientis standing. This film can be used to determine the femoral and tibialanatomical axes and to estimate the biomechanical axes. As will beappreciated by those of skill in the art, these processes foridentifying, e.g., anatomical and biomechanical axis of the joint can beapplied to other joints without departing from the scope of theinvention.

Anatomical and biomechanical axes can also be determined using otherimaging modalities, including but not limited to, computed tomographyand MRI. For example, a CT scan can be obtained through the hip joint,the knee joint, and the ankle joint. Optionally, the scan can bereformatted in the sagittal, coronal, or other planes. The CT images canthen be utilized to identify anatomical landmarks and to determine theanatomical and biomechanical axes of the hip joint, knee joint, and/orankle joint.

Similarly, an MRI scan can be obtained for this purpose. For example, anMRI scan of the thigh and pelvic region can be obtained using a bodycoil or a torso phased array coil. A high resolution scan of the kneejoint can be obtained using a dedicated extremity coil. A scan of thecalf/tibia region and the ankle joint can be obtained again using a bodycoil or a torso phased array coil. Anatomical landmarks can beidentified in each joint on these scans and the anatomical andbiomechanical axes can be estimated using this information.

In various embodiments, the imaging scan can be extended for 5 cm, morepreferably 10 cm, or more preferably 15 cm above and/or below the jointthereby deriving anatomic information that can be used to derive theanatomic and biomechanical axis. For example, an MRI or CT scan can beobtained through a knee joint. The scan can extend 15 cm above and belowthe joint. The mid-femoral line and mid-tibial line as well as otheranatomic landmarks such as the femoral transepicondylar line orWhiteside line or posterior condylar line can be determined and can beused to estimate the anatomic and biomechanical axes. Thus, in theexample of a knee joint, no additional scanning through the hip jointand ankle joints will be needed.

With, for example, MRI, even larger coverage may be obtained, forexample with a series of axial, sagittal or coronal slices obtained witha large field of view, e.g. 20 cm or more preferably 25 cm, or morepreferably 30 cm, or more preferably 35 cm. These large field of viewscans can be utilized to estimate the anatomic and biomechanical axes asdescribed above. They lack, however, information on the surface detailof the joint due to limitations in spatial resolution. A second oradditional scan can be performed with high resolution, e.g. with spatialresolution and x and y axis of less than 1.0 mm, or, more preferably,less than 0.8 mm, or, more preferably, less than 0.6 mm. The additionalhigh resolution scan may be utilized to derive the articular surfacedetail needed for a good and accurate fit between the guidance templateor implant, and the articular surface or adjacent structures.

A biomechanical axis and, in some instances, an anatomical axis mayadvantageously be defined by imaging the entire extremity in question.Such imaging may include cross-sectional, spiral or volumetric imagingvia a CT or MRI scan or optical imaging through the entire extremity, oracquisition of select images or slices or volumes through an area ofinterest such as a hip joint, a knee joint or ankle joint.

In an illustrative embodiment, scans through the entire or portions ofan entire extremity covering multiple joints may be replaced with anextended scan through a single joint such as a knee joint. For example,it may not be sufficient to estimate a biomechanical axis or ananatomical access with a standard knee scan such as a CT scan or MRIscan that includes, for example, only ten centimeter of the area orvolume of interest above, or ten centimeters of area or volume ofinterest below the tibiofemoral joints space. With an extended scan, alarger area adjacent to the target joint can be included in the scan,e.g. fifteen centimeters above and below the medial tibia femoral jointspace, twenty centimeters above and below the medial tibia femoral jointspace, fifteen centimeters above and twenty centimeters below the medialtibiofemoral joint space, twenty centimeters above and twenty-fivecentimeters below the medial tibiofemoral joint space. While theextended scan is less involved on the operative side than the scaninvolving the neighboring joints, it can, optionally be used to providean estimate of the anatomical axis, biomechanical axis, and/or animplant axes or related planes. Thus, better ease of use is provided atthe expense of, possibly, more radiation and possibly, less accuracy.

In another embodiment, cross-sectional or volumetric images such as CTscans or MRI scans may be acquired through more than one joint,typically one or more joints neighboring the one contemplated forsurgery. For example, CT or MRI slices, CT spirals, CT or MRI volumes,MRI two plane acquisitions with optional image fusion, or othertomographic acquisitions are acquired through the hip joint, knee jointand ankle joint in a patient scheduled for total knee replacementsurgery. The 3D surgical guidance templates may be optimized by usinganatomic and/or biomechanical information obtained in the adjacentneighboring joints, for example, resulting in an improved anatomic orfunctional result. By using cross-sectional or volumetric imaginginformation, more accurate identification of anatomic landmarks foridentifying relevant anatomical and/or biomechanical axis, relevantplanes including surgical planes and implant planes, as well as implantaxes can be achieved when compared to x-rays or CT scout scans, inparticular when the cross-sectional or volumetric data are acquiredthrough neighboring joints. The accuracy of the position, orientation,shape or combinations thereof, of a 3D guide template can thus beimproved with resulting improvement in accuracy of the surgicalcorrection of underlying deformities such as varus, valgus, abduction,adduction, or rotation deformities.

An imaging test obtained during weight-bearing conditions has someinherent advantages, in that it demonstrates normal as well aspathological loading and load distribution. A cross-sectional imagingstudy such as a CT scan or MRI scan has some advantages because itallows one to visualize and demonstrate the anatomical landmarks inthree, rather than two, dimensions, thereby adding accuracy. Moreover,measurements can be performed in other planes, such as the sagittal oroblique planes, that may not be easily accessible in certain anatomicalregions using conventional radiography. In principle, any imaging testcan be utilized for this purpose.

The biomechanical axis can be defined as the axis going from the centerof the femoral head, between the condylar surfaces and through the anklejoint

The software may automatically, semi-automatically or manually assistedfind or identify the relevant anatomic points to calculate the anatomicand biomechanical axes, in accordance with various embodiments of theinvention. For example, the software or the user can find the center ofthe femoral head. Optionally, this can be done in 3D rather than only in2D. Thus, for example, in the femoral head, the software can find thecenter of the femoral head relative to its x, y, and z-dimensions.Alternatively, the relevant anatomic points can be selected manually andthe axes can be calculated.

In another embodiment the software can compute methods of adjustingvarus or valgus or ante- or retroversion deformity or rotationaldeformity based on such anatomic and biomechanical axis measurements.For example, the surface of a surgical guide template can be adapted sothat surgical cuts performed for a total knee implant can be placed tocorrect an underlying varus or valgus deformity or, for example, ante-or retroversion. Alternatively, the openings/cut planes of a surgicalguide template used for drilling, cutting and the like can be adjustedto achieve a varus or valgus correction to a near anatomic orphysiologic range. These adjustments can be optimized for the implantsof different manufacturers, e.g. Johnson&Johnson, Stryker, Smith&Nephew,Biomet and Zimmer.

In various embodiments, gait, loading and other physical activities of ajoint as well as static joint positions may be simulated using acomputer workstation. The template and its apertures and the resultantsurgical templates and/or procedures, e.g. cuts, drilling, rasping, maybe optimized using this information to achieve an optimal functionalresult. For example, the template and its apertures and the resultantimplant position may be optimized for different degrees of flexion andextension, internal or external rotation, abduction or adduction, andante or retroversion. Thus, the templates may be used to achieve motionthat is optimized in one, two or more directions. Not only anatomic, butalso functional optimization is possible in this manner.

The origin and insertion of ligaments, e.g. the anterior and posteriorcruciate ligaments and the medial and lateral collateral ligaments inthe case of a knee, can be visualized on the scan. With MRI, theligaments are directly visible. If the ligament is torn, the location ofthe residual fibers at the origin or attachment can be visualized.Different joint positions can then be simulated and changes in ligamentlength can be determined for different angles of flexion and extension,internal or external rotation, abduction or adduction, and ante orretroversion. These simulations can be performed without but also withthe implant in place. Thus, ligament length—and through this presumedtension—can be estimated virtually with any given implant and implantsize. Different implants or component(s) can be tested preoperatively onthe computer workstation and the implant or component(s) yielding theoptimal ligament performance, e.g. minimal change in ligament length,for different joint positions can be determined pre-operatively. Thus,the invention provides among others for pre-operative ligamentbalancing, including but not limited to by directly visualizing theligaments or fiber remnants.

For example, in one embodiment a loading apparatus may be applied to thepatient to simulate weight-bearing while acquiring the CT scan. Anon-limiting example of such a loading apparatus has been described byDynamed with the Dynawell device. Any loading apparatus that can applyaxial or other physiologic or near physiologic loading forces on thehip, knee or ankle joints or two or three of them may be used. Othermore sophisticated scanning procedures can be used to derive thisinformation without departing from the scope of the invention.

In a preferred embodiment, when imaging a joint of the lower extremity,a standing, weight-bearing x-ray can be obtained to determine thebiomechanical axis. In the case of a knee or hip joint, for example, astanding, weight-bearing x-ray of the hip joint or the knee joint can beobtained. Alternatively, standing, weight-bearing x-rays can be obtainedspanning the entire leg from the hip to the foot. The x-ray can beobtained in the antero-posterior or posterior-anterior projection butalso in a lateral projection or principally any other projection that isdesired. The user can measure the biomechanical axis, for example, byfinding the centroid of the femoral head and the centroid of the anklejoint and by connecting these. This measurement can be performedmanually, for example, on a x-ray film or electronically, for example,on a digitized or digital image, including with software assistance. Theaxis measured on the standing, weight-bearing x-ray can be crossreferenced with another imaging modality such a CT or MRI scan. Forexample, a biomechanical axis can be determined on a standing x-ray ofthe leg. The result and data can be cross referenced, for example, byidentifying corresponding bony anatomical landmarks to a CT scan or MRIscan. The result and information can then be utilized to determine theoptimal shape of a 3-D guidance template. Specifically, the orientation,position, or shape of the template can be influenced based on themeasurement of the biomechanical axis. Moreover, the position or shapeof any blocks attached to said templates or linkages or the position orshape instruments attached to the mold, block or linkages can beinfluenced by this measurement. Combining the standing, weight-bearingimaging modality with CT scanning or MRI scanning has the principleadvantage that the joint is evaluated during physiological loading. CTor MRI alone, typically do not afford assessment in loaded,weight-bearing condition.

As described above, the biomechanical axis can be evaluated in differentplanes or in three dimensions. For example, the actual biomechanicalaxis can be assessed in the AP plane and a desired biomechanical axiscan be determined in this plane. In addition, the actual biomechanicalaxis can be determined in the lateral plane, for example, in the lateralprojection radiograph, and the desired biomechanical axis can bedetermined in the lateral plane. By measuring the relevant biomechanicaland anatomical axis in two or more planes, the shape of a 3-D guidancetemplate and/or implant can be further refined and optimized with resultin improvements in clinical and patient function.

The biomechanical or anatomical axis may also be measured using otherapproaches including a non-weight bearing position. For example,anatomical landmarks can be identified on a CT scout scan and crossreferenced to a joint such as a knee joint or a hip joint for whichsurgery is contemplated. Thus, for example, the user can measure anddetermine the centroid of the ankle joint and the centroid of the hipjoint for knee surgery using the CT scout scan.

In a preferred embodiment, the anatomical landmarks are determined usingCT slices or MRI slices rather than a scout scan. A CT scout scan or MRIscout scan can have inherent limitations in spatial resolution. A CTscout scan is typically a single, 2-D radiographic image of theextremity lacking 3-D anatomical information and lacking high spatialresolution. An MRI scout scan is typically composed of multiple 2-D MRIslices, possibly acquired in one, two, or three planes. However, theresolution of the MRI scout scan is typically also limited. By acquiringselective slices and even isotropic or near isotropic data sets throughneighboring joints, anatomical landmarks can be identified in a morereliable manner thereby improving the accuracy of anatomical andbiomechanical axis determination. This improvement in accuracytranslates into an improvement in accuracy in the resultant 3-D guidancemold, for example, a knee or hip joint, including improved accuracy ofits shape, orientation, or position.

Computed Tomography imaging has been shown to be highly accurate for thedetermination of the relative anatomical and biomechanical axes of theleg (Testi Debora, Zannoni Cinzia, Cappello Angelo and Viceconti Marco.“Border tracing algorithm implementation for the femoral geometryreconstruction.” Comp. Meth. and Programs in Biomed., Feb. 14, 2000;Farrar M J, Newman R J, Mawhinney R R, King R. “Computed tomography scanscout film for measurement of femoral axis in knee arthroplasty.” J.Arthroplasty. 1999 December; 14(8): 1030-1; Kim J S, Park T S, Park S B,Kim J S, Kim I Y, Kim S I. “Measurement of femoral neck anteversion in3D. Part 1: 3D imaging method.” Med. and Biol. Eng. and Computing.38(6): 603-609, November 2000; Akagi M, Yamashita E, Nakagawa T, AsanoT, Nakamura T. “Relationship between frontal knee alignment andreference axis in the distal femur.” Clin. Ortho. and Related Res. No.388,147-156, 2001; Mahaisavariya B, Sitthiseripratip K, Tongdee T, BohezE, Sloten J V, Oris P. “Morphological study of the proximal femur: a newmethod of geometrical assessment using 3 dimensional reverseengineering.” Med. Eng. and Phys. 24 (2002) 617-622; Lam Li On,Shakespeare D. “Varus/Valgus alignment of the femoral component in totalknee arthroplasty.” The Knee, 10 (2003) 237-241).

The angles of the anatomical structures of the proximal and distal femuralso show a certain variability level (i.e. standard deviation)comparable with the varus or valgus angle or the angle between theanatomical femoral axis and the biomechanical axis (Mahaisavariya B,Sitthiseripratip K, Tongdee T, Bohez E, Sloten J V, Oris P.“Morphological study of the proximal femur: a new method of geometricalassessment using 3 dimensional reverse engineering.” Med. Eng. and Phys.24 (2002) 617-622). Thus, a preferred approach for assessing the axes isbased on CT scans of the hip, knee and ankle joint or femur rather thanonly of the knee region.

CT has been shown to be efficient in terms of the contrast of the bonetissue with respect to surrounding anatomical tissue so the bonestructures corresponding to the femur and tibia can be extracted veryaccurately with semi automated computerized systems (Mahaisavariya B,Sitthiseripratip K, Tongdee T, Bohez E, Sloten J V, Oris P.“Morphological study of the proximal femur: a new method of geometricalassessment using 3 dimensional reverse engineering.” Med. Eng. and Phys.24 (2002) 617-622; Testi Debora, Zannoni Cinzia, Cappello Angelo andViceconti Marco. “Border tracing algorithm implementation for thefemoral geometry reconstruction.” Comp. Meth. and Programs in Biomed.,Feb. 14, 2000).

While 2-D CT has been shown to be accurate in the estimation of thebiomechanical axis (Mahaisavariya B, Sitthiseripratip K, Tongdee T,Bohez E, Sloten J V, Oris P. “Morphological study of the proximal femur:a new method of geometrical assessment using 3 dimensional reverseengineering.” Med. Eng. and Phys. 24 (2002) 617-622; Testi Debora,supra.; Lam Li On, Supra, 3-D CT has been shown to be more accurate forthe estimation of the femoral anteversion angle (Kim J S, Park T S, ParkS B, Kim J S, Kim I Y, Kim S I. Measurement of femoral neck anteversionin 3D. Part 1: 3D imaging method. Medical and Biological engineering andcomputing. 38(6): 603-609, November 2000; Kim J S, Park T S, Park S B,Kim J S, Kim I Y, Kim S I. Measurement of femoral neck anteversion in3D. Part 1: 3D modeling method. Medical and Biological engineering andcomputing. 38(6): 610-616, November 2000). Farrar used simple CT 2-Dscout views to estimate the femoral axis (Farrar M J, Newman R J,Mawhinney R R, King R. Computed tomography scan scout film formeasurement of femoral axis in knee arthroplasty. J. Arthroplasty. 1999December; 14(8): 1030-1).

In one embodiment, 2-D sagittal and coronal reconstructions of CT sliceimages are used to manually estimate the biomechanical axis. One skilledin the art can easily recognize many different ways to automate thisprocess. For example, a CT scan covering at least the hip, knee andankle region is acquired. This results in image slices (axial) which canbe interpolated to generate the sagittal and coronal views.

Preprocessing (filtering) of the slice images can be used to improve thecontrast of the bone regions so that they can be extracted accuratelyusing simple thresholding or a more involved image segmentation toollike LiveWire or active contour models.

Identification of landmarks of interest like the centroid of the tibialshaft, the ankle joint, the intercondylar notch and the centroid of thefemoral head can be performed. The biomechanical axis can be defined asthe line connecting the proximal and the distal centroids, i.e. thefemoral head centroid, the tibial or ankle joint centroid. The positionof the intercondylar notch can be used for evaluation of possibledeviations, errors or deformations including varus and valgus deformity.

In one embodiment, multiple imaging tests can be combined. For example,the anatomical and biomechanical axes can be estimated using aweight-bearing x-ray of the extremity or portions of the extremity. Theanatomical information derived in this fashion can then be combined witha CT or MRI scan of one or more joints, such as a hip, knee, or anklejoint. Landmarks seen on radiography can then, for example, becross-referenced on the CT or MRI scan. Axis measurements performed onradiography can be subsequently applied to the CT or MRI scans or otherimaging modalities. Similarly, the information obtained from a CT scancan be compared with that obtained with an MRI or ultrasound scan. Inone embodiment, image fusion of different imaging modalities can beperformed. For example, if surgery is contemplated in a knee joint, afull-length weight-bearing x-ray of the lower extremity can be obtained.This can be supplemented by a spiral CT scan, optionally withintra-articular contrast of the knee joint providing high resolutionthree-dimensional anatomical characterization of the knee anatomy evenincluding the menisci and cartilage. This information, along with theaxis information provided by the radiograph can be utilized to select orderive therapies, such as implants or surgical instruments.

In certain embodiments, it may be desirable to characterize the shapeand dimension of intra-articular structures, including subchondral boneor the cartilage. This may be done, for example, by using a CT scan,preferably a spiral CT scan of one or more joints. The spiral CT scancan optionally be performed using intra-articular contrast.Alternatively, an MRI scan can be performed. If CT is utilized, a fullspiral scan, or a few selected slices, can be obtained throughneighboring joints. Typically, a full spiral scan providing fullthree-dimensional characterization would be obtained in the joint forwhich therapy is contemplated. If implants, or templates, for surgicalinstruments are selected or shaped, using this scan, the subchondralbone shape can be accurately determined from the resultant image data. Astandard cartilage thickness and, similarly, a standard cartilage losscan be assumed in certain regions of the articular surface. For example,a standard thickness of 2 mm of the articular cartilage can be appliedto the subchondral bone in the anterior third of the medial and lateralfemoral condyles. Similarly, a standard thickness of 2 mm of thearticular cartilage can be applied to the subchondral bone in theposterior third of the medial and lateral femoral condyles. A standardthickness of 0 mm of the articular cartilage can be applied in thecentral weight-bearing zone of the medial condyle, and a different valuecan be applied to the lateral condyle. The transition between thesezones can be gradual, for example, from 2 mm to 0 mm. These standardvalues of estimated cartilage thickness and cartilage loss in differentregions of the joint can optionally be derived from a referencedatabase. The reference database can include categories such as age,body mass index (“BMI”), severity of disease, pain, severity of varusdeformity, severity of valgus deformity, Kellgren-Lawrence score, alongwith other parameters that are determined to be relative and useful. Useof a standard thickness for the articular cartilage can facilitate theimaging protocols required for pre-operative planning.

Alternatively, however, the articular cartilage can be fullycharacterized by performing a spiral CT scan of the joint in thepresence of intra-articular contrast or by performing an MRI scan usingcartilage sensitive pulse sequences.

The techniques described herein can be used to obtain an image of ajoint that is stationary, either weight bearing or not, or in motion orcombinations thereof. Imaging studies that are obtained during jointmotion can be useful for assessing the load bearing surface. This can beadvantageous for designing or selecting implants, e.g. for selectingreinforcements in high load areas, for surgical tools and for implantplacement, e.g. for optimizing implant alignment relative to high loadareas.

iii. Joint Space

In accordance with another embodiment of the invention, a method andsystem for determining joint space width is provided, in accordance withan embodiment of the invention. Without limitation, a CT scan, MRI scan,optical scan, and/or ultrasound imaging is performed. The medial andlateral joint space width in a knee joint, the joint space in a hipjoint, ankle joint or other joint is evaluated. This evaluation may beperformed in two dimensions, using a single scan plane orientation, suchas sagittal or coronal plane, or it may be performed in threedimensions. The evaluation of joint space width may include measuringthe distance from the subchondral bone plate of one articular surface tothe subchondral bone plate of the opposing articular surface.Alternatively, the cartilage thickness may be measured directly on oneor more articular surfaces. Joint space width or cartilage thickness maybe measured for different regions of the joint and joint space width andcartilage loss can be evaluated in anterior, posterior, medial, lateral,superior and/or inferior positions. The measurements may be performedfor different positions of the joint such as a neutral position, 45degrees of flexion, 90 degrees of flexion, 5 degrees of abduction, 5degrees of internal rotation and so forth. For example, in a knee joint,the joint space width may be evaluated in extension and at 25 degrees ofknee flexion and 90 degrees of knee flexion. The medial and lateraljoint space width may be compared and differences in medial and lateraljoint space width can be utilized to optimize the desired postoperativecorrection in anatomical or biomechanical axis alignment based on thisinformation. The shape, orientation, or position of a 3D guided templatemay be adjusted using this information, for example, in knee or hipimplant placement or other surgeries.

For example, the measurement may show reduced joint space width orcartilage thickness in the medial compartment when compared to a normalanatomic reference standard, e.g. from age or sex or gender matchedcontrols, and/or lateral compartment. This can coincide with valgusalignment of the knee joint, measured, for example, on the scout scan ofan CT-scan or the localizer scan of an MRI scan including multiplelocalizer scans through the hip, knee and ankle joints.

If the biomechanical axis estimated on the comparison of the medial andlateral joint space width coincides with the biomechanical axis of theextremity measured on the scout scan, no further adjustment may benecessary. If the biomechanical axis estimated on the comparison of themedial and lateral joint space width does not coincide with thebiomechanical axis of the extremity measured on the CT or MRI scoutscan, additional correction of the valgus deformity (or in otherembodiments, varus or other deformities) can be achieved.

This additional correction may be determined, for example, by adding thedifference in axis correction desired based on biomechanical axismeasured by comparison of the medial lateral joint space width and axiscorrection desired based on measurement of the biomechanical axis of theextremity measured on the scout or localizer scan to axis correctiondesired based on measurement of the biomechanical axis of the extremitymeasured on the scout or localizer scan alone. By combining theinformation from both, measurement of joint space width of the medianand lateral compartment and measurement of the biomechanical axis usingthe scout scan or localizer scan or, for example, a weight bearingx-ray, an improved assessment of axis alignment during load bearingconditions can be obtained with resultant improvements in the shape,orientation or position of the 3D guidance template and relatedattachments or linkages.

Optionally, the extremity can be loaded while in the scanner, forexample, using a compression harness. Examples for compression harnesseshave been published, for example, by Dynawell.

iv. Estimation of Cartilage Loss

In another embodiment, an imaging modality such as spiral CT, spiral CTarthography, MRI, optical imaging, optical coherence tomography,ultrasound and others may be used to estimate cartilage loss in one, twoor three dimensions. The information can be used to determine a desiredcorrection of a measured biomechanical or anatomical axis. Thecorrection can be in the anterior-posterior, medio-lateral, and/orsuper-inferior direction, or any other direction applicable ordesirable, or combinations thereof. The information can be combined withother data e.g., from a standing, weight bearing x-ray or CT scout scan,or an MRI localizer scan or a CT scan or MRI scan that includesaxial/spiral or other images through the hip, knee and ankle joints. Theinformation can be used to refine the axis correction desired based on,for example, standing x-rays, non-weight bearing x-rays, CT scout scans,MRI localizer scans and the like.

In another embodiment, any axis correction can be performed in a singleplane (e.g., the medial-lateral plane), in two planes (e.g., the mediallateral and anterior-posterior planes), or multiple planes, includingoblique planes that are biomechanically or anatomically relevant ordesirable.

v. High Resolution Imaging

Additional improvements in accuracy of the 3D guide template and/orimplants surfaces may be obtained with use of imaging technology thatyields high spatial resolution, not only within the imaging plane, butalong all three planes, specifically the X, Y and Z axis. With CTscanning, this can be achieved with the advent of spiral CT Scanningtechniques. With MRI, dual or more plane scanning or volumetricacquisition can be performed. If dual or more plane MRI scanning isperformed, these multiple scan planes can be fused, for example bycross-registration and resampling along the X, Y and Z axis. Theresultant effective resolution in X, Y and Z direction is greatlyimproved as compared to standard CT scanning or standard MRI scanning.Improvements in resolution have the advantage that the resultant 3Dguide templates can be substantially more accurate, for example withregard to their position, shape or orientation.

vi. Phantom Scans

Imaging modalities are subject to scan to scan variations, for example,including spatial distortion. In one embodiment, phantom scans may beperformed in order to optimize the scan quality, specifically spatialresolution and spatial distortion. A phantom scan can be performed priorto a patient scan, simultaneously with a patient scan or after a patientscan. Using the phantom scan data, it is possible to make adjustmentsand optimizations of the scanner and, moreover, to perform image postprocessing to perform corrections, for example, correction of geometricdistortions. Thus, if a phantom scan detects certain geometricdistortion in the X, Y or Z axis and the amount of distortion ismeasured on the phantom scan, a correction factor can be included in thedata prior to generating a 3D guide template. The resulting 3D guidetemplate is thus more accurate with resulting improvement inintra-operative cross-reference to the anatomic surface and resultantimproved accuracy in any surgical intervention such as drilling orcutting.

In another embodiment, a smoothing operation, e.g. using low frequencyfiltering, can be performed in order to remove any image relatedartifacts, such as stepping artifacts between adjacent CT or MRI slices.In some applications, the smoothing operation can be helpful inimproving the fit between the joint and the template.

B. Intraoperative Measurements

Alternatively, or in addition to, non-invasive imaging techniquesdescribed above, measurements of the size of an area of diseasedcartilage or an area of cartilage loss, measurements of cartilagethickness and/or curvature of cartilage or bone can be obtainedintraoperatively during arthroscopy or open arthrotomy. Intraoperativemeasurements can, but need not, involve actual contact with one or moreareas of the articular surfaces.

Devices suitable for obtaining intraoperative measurements of cartilageor bone or other articular structures, and to generate a topographicalmap of the surface include but are not limited to, Placido disks,optical measurements tools and device, optical imaging tools anddevices, and laser interferometers, and/or deformable materials ordevices. (See, for example, U.S. Pat. No. 6,382,028 to Wooh et al.,issued May 7, 2002; U.S. Pat. No. 6,057,927 to Levesque et al., issuedMay 2, 2000; U.S. Pat. No. 5,523,843 to Yamane et al. issued Jun. 4,1996; U.S. Pat. No. 5,847,804 to Sarver et al. issued Dec. 8, 1998; andU.S. Pat. No. 5,684,562 to Fujieda, issued Nov. 4, 1997).

FIG. 3A illustrates a Placido disk of concentrically arranged circles oflight. The concentric arrays of the Placido disk project well-definedcircles of light of varying radii, generated either with laser or whitelight transported via optical fiber. The Placido disk can be attached tothe end of an endoscopic device (or to any probe, for example ahand-held probe) so that the circles of light are projected onto thecartilage surface. FIG. 3B illustrates an example of a Placido diskprojected onto the surface of a fixed curvature. One or more imagingcameras can be used (e.g., attached to the device) to capture thereflection of the circles. Mathematical analysis is used to determinethe surface curvature. The curvature can then, for example, bevisualized on a monitor as a color-coded, topographical map of thecartilage surface. Additionally, a mathematical model of thetopographical map can be used to determine the ideal surface topographyto replace any cartilage defects in the area analyzed.

FIG. 4 shows a reflection resulting from the projection of concentriccircles of light (Placido disk) on each femoral condyle, demonstratingthe effect of variation in surface contour on reflected circles.

Similarly an optical imaging device or measurement tool, e.g. a laserinterferometer, can also be attached to the end of an endoscopic device.Optionally, a small sensor can be attached to the device in order todetermine the cartilage surface or bone curvature using phase shiftinterferometry, producing a fringe pattern analysis phase map (wavefront) visualization of the cartilage surface. The curvature can then bevisualized on a monitor as a color coded, topographical map of thecartilage surface. Additionally, a mathematical model of thetopographical map can be used to determine the ideal surface topographyto replace any cartilage or bone defects in the area analyzed. Thiscomputed, ideal surface, or surfaces, can then be visualized on themonitor, and can be used to select the curvature, or curvatures, of thereplacement cartilage or mold.

Optical imaging techniques can be utilized to generate a 3Dvisualization or surface map of the cartilage or bone, which can be usedto generate an articular repair system or a mold.

One skilled in the art will readily recognize that other techniques foroptical measurements of the cartilage surface curvature can be employedwithout departing from the scope of the invention. For example, a2-dimensional or 3-dimensional map, such as that shown in FIG. 5 andFIG. 6, can be generated.

Mechanical devices (e.g., probes) can also be used for intraoperativemeasurements, for example, deformable materials such as gels, molds, anyhardening materials (e.g., materials that remain deformable until theyare heated, cooled, or otherwise manipulated). See, e.g., WO 02/34310 toDickson et al., published May 2, 2002. For example, a deformable gel canbe applied to a femoral condyle. The side of the gel pointing towardsthe condyle can yield a negative impression of the surface contour ofthe condyle. The negative impression can then be used to determine thesize of a defect, the depth of a defect and the curvature of thearticular surface in and adjacent to a defect. This information can beused to select a therapy, e.g. an articular surface repair system or amold. It can also be used to make a mold, either directly with use ofthe impression or, for example, indirectly via scanning the impression.In another example, a hardening material can be applied to an articularsurface, e.g. a femoral condyle or a tibial plateau. The hardeningmaterial can remain on the articular surface until hardening hasoccurred. The hardening material can then be removed from the articularsurface. The side of the hardening material pointing towards thearticular surface can yield a negative impression of the articularsurface. The negative impression can then be used to determine the sizeof a defect, the depth of a defect and the curvature of the articularsurface in and adjacent to a defect. This information can then be usedto select a therapy, e.g. an articular surface repair system or a mold.It can also be used to make a mold, either directly with use of theimpression or, for example, indirectly via scanning the impression. Insome embodiments, the hardening system can remain in place and form theactual articular surface repair system.

In certain embodiments, the deformable material comprises a plurality ofindividually moveable mechanical elements. When pressed against thesurface of interest, each element can be pushed in the opposingdirection and the extent to which it is pushed (deformed) can correspondto the curvature of the surface of interest. The device can include abrake mechanism so that the elements are maintained in the position thatconforms to the surface of the cartilage and/or bone. The device canthen be removed from the patient and analyzed for curvature.Alternatively, each individual moveable element can include markersindicating the amount and/or degree it is deformed at a given spot. Acamera can be used to intra-operatively image the device and the imagecan be saved and analyzed for curvature information. Suitable markersinclude, but are not limited to, actual linear measurements (metric orempirical), different colors corresponding to different amounts ofdeformation and/or different shades or hues of the same color(s).Displacement of the moveable elements can also be measured usingelectronic means.

Other devices to measure cartilage and subchondral bone intraoperativelyinclude, for example, ultrasound probes. An ultrasound probe, preferablyhandheld, can be applied to the cartilage and the curvature of thecartilage and/or the subchondral bone can be measured. Moreover, thesize of a cartilage defect can be assessed and the thickness of thearticular cartilage can be determined. Such ultrasound measurements canbe obtained in A-mode, B-mode, or C-mode. If A-mode measurements areobtained, an operator can typically repeat the measurements with severaldifferent probe orientations, e.g. mediolateral and anteroposterior, inorder to derive a three-dimensional assessment of size, curvature andthickness.

One skilled in the art will easily recognize that different probedesigns are possible using the optical, laser interferometry, mechanicaland ultrasound probes. The probes are preferably handheld. In certainembodiments, the probes or at least a portion of the probe, typicallythe portion that is in contact with the tissue, can be sterile.Sterility can be achieved with use of sterile covers, for examplesimilar to those disclosed in WO 99/08598A1 to Lang, published Feb. 25,1999.

Analysis on the curvature of the articular cartilage or subchondral boneusing imaging tests and/or intraoperative measurements can be used todetermine the size of an area of diseased cartilage or cartilage loss.For example, the curvature can change abruptly in areas of cartilageloss. Such abrupt or sudden changes in curvature can be used to detectthe boundaries of diseased cartilage or cartilage defects.

As described above, measurements can be made while the joint isstationary, either weight bearing or not, or in motion.

II. Repair Materials

A wide variety of materials find use in the practice of the presentinvention, including, but not limited to, plastics, metals, crystal freemetals, ceramics, biological materials (e.g., collagen or otherextracellular matrix materials), hydroxyapatite, cells (e.g., stemcells, chondrocyte cells or the like), or combinations thereof. Based onthe information (e.g., measurements) obtained regarding the defect andthe articular surface and/or the subchondral bone, a repair material canbe formed or selected. Further, using one or more of these techniquesdescribed herein, a cartilage replacement or regenerating materialhaving a curvature that will fit into a particular cartilage defect,will follow the contour and shape of the articular surface, and willmatch the thickness of the surrounding cartilage. The repair materialcan include any combination of materials, and typically include at leastone non-pliable material, for example materials that are not easily bentor changed.

A. Metal and Polymeric Repair Materials

Currently, joint repair systems often employ metal and/or polymericmaterials including, for example, prostheses which are anchored into theunderlying bone (e.g., a femur in the case of a knee prosthesis). See,e.g., U.S. Pat. No. 6,203,576 to Afriat, et al. issued Mar. 20, 2001 andU.S. Pat. No. 6,322,588 to Ogle, et al. issued Nov. 27, 2001, andreferences cited therein. A wide-variety of metals are useful in thepractice of the present invention, and can be selected based on anycriteria. For example, material selection can be based on resiliency toimpart a desired degree of rigidity. Non-limiting examples of suitablemetals include silver, gold, platinum, palladium, iridium, copper, tin,lead, antimony, bismuth, zinc, titanium, cobalt, stainless steel,nickel, iron alloys, cobalt alloys, such as Elgiloy®, acobalt-chromium-nickel alloy, and MP35N, anickel-cobalt-chromium-molybdenum alloy, and Nitinol™, a nickel-titaniumalloy, aluminum, manganese, iron, tantalum, crystal free metals, such asLiquidmetal® alloys (available from LiquidMetal Technologies,www.liquidmetal.com), other metals that can slowly form polyvalent metalions, for example to inhibit calcification of implanted substrates incontact with a patient's bodily fluids or tissues, and combinationsthereof.

Suitable synthetic polymers include, without limitation, polyamides(e.g., nylon), polyesters, polystyrenes, polyacrylates, vinyl polymers(e.g., polyethylene, polytetrafluoroethylene, polypropylene andpolyvinyl chloride), polycarbonates, polyurethanes, poly dimethylsiloxanes, cellulose acetates, polymethyl methacrylates, polyether etherketones, ethylene vinyl acetates, polysulfones, nitrocelluloses, similarcopolymers and mixtures thereof. Bioresorbable synthetic polymers canalso be used such as dextran, hydroxyethyl starch, derivatives ofgelatin, polyvinylpyrrolidone, polyvinyl alcohol,poly[N-(2-hydroxypropyl)methacrylamide], poly(hydroxy acids),poly(epsilon-caprolactone), polylactic acid, polyglycolic acid,poly(dimethyl glycolic acid), poly(hydroxy butyrate), and similarcopolymers can also be used.

Other materials would also be appropriate, for example, the polyketoneknown as polyetheretherketone (PEEK™). This includes the material PEEK450G, which is an unfilled PEEK approved for medical implantationavailable from Victrex of Lancashire, Great Britain. (Victrex is locatedat www.matweb.com or see Boedeker www.boedeker.com). Other sources ofthis material include Gharda located in Panoli, India(www.ghardapolymers.com).

It should be noted that the material selected can also be filled. Forexample, other grades of PEEK are also available and contemplated, suchas 30% glass-filled or 30% carbon filled, provided such materials arecleared for use in implantable devices by the FDA, or other regulatorybody. Glass filled PEEK reduces the expansion rate and increases theflexural modulus of PEEK relative to that portion which is unfilled. Theresulting product is known to be ideal for improved strength, stiffness,or stability. Carbon filled PEEK is known to enhance the compressivestrength and stiffness of PEEK and lower its expansion rate. Carbonfilled PEEK offers wear resistance and load carrying capability.

As will be appreciated, other suitable similarly biocompatiblethermoplastic or thermoplastic polycondensate materials that resistfatigue, have good memory, are flexible, and/or deflectable have verylow moisture absorption, and good wear and/or abrasion resistance, canbe used without departing from the scope of the invention. The implantcan also be comprised of polyetherketoneketone (PEKK).

Other materials that can be used include polyetherketone (PEK),polyetherketoneetherketoneketone (PEKEKK), andpolyetheretherketoneketone (PEEKK), and generally apolyaryletheretherketone. Further other polyketones can be used as wellas other thermoplastics.

Reference to appropriate polymers that can be used for the implant canbe made to the following documents, all of which are incorporated hereinby reference. These documents include: PCT Publication WO 02/02158 A1,dated Jan. 10, 2002 and entitled Bio-Compatible Polymeric Materials; PCTPublication WO 02/00275 A1, dated Jan. 3, 2002 and entitledBio-Compatible Polymeric Materials; and PCT Publication WO 02/00270 A1,dated Jan. 3, 2002 and entitled Bio-Compatible Polymeric Materials.

The polymers can be prepared by any of a variety of approaches includingconventional polymer processing methods. Preferred approaches include,for example, injection molding, which is suitable for the production ofpolymer components with significant structural features, and rapidprototyping approaches, such as reaction injection molding andstereolithography. The substrate can be textured or made porous byeither physical abrasion or chemical alteration to facilitateincorporation of the metal coating. Other processes are alsoappropriate, such as extrusion, injection, compression molding and/ormachining techniques. Typically, the polymer is chosen for its physicaland mechanical properties and is suitable for carrying and spreading thephysical load between the joint surfaces.

More than one metal and/or polymer can be used in combination with eachother. For example, one or more metal-containing substrates can becoated with polymers in one or more regions or, alternatively, one ormore polymer-containing substrate can be coated in one or more regionswith one or more metals.

The system or prosthesis can be porous or porous coated. The poroussurface components can be made of various materials including metals,ceramics, and polymers. These surface components can, in turn, besecured by various means to a multitude of structural cores formed ofvarious metals. Suitable porous coatings include, but are not limitedto, metal, ceramic, polymeric (e.g., biologically neutral elastomerssuch as silicone rubber, polyethylene terephthalate and/or combinationsthereof) or combinations thereof. See, e.g., U.S. Pat. No. 3,605,123 toHahn, issued Sep. 20, 1971. U.S. Pat. No. 3,808,606 to Tronzo issued May7, 1974 and U.S. Pat. No. 3,843,975 to Tronzo issued Oct. 29, 1974; U.S.Pat. No. 3,314,420 to Smith issued Apr. 18, 1967; U.S. Pat. No.3,987,499 to Scharbach issued Oct. 26, 1976; and GermanOffenlegungsschrift 2,306,552. There can be more than one coating layerand the layers can have the same or different porosities. See, e.g.,U.S. Pat. No. 3,938,198 to Kahn, et al., issued Feb. 17, 1976.

The coating can be applied by surrounding a core with powdered polymerand heating until cured to form a coating with an internal network ofinterconnected pores. The tortuosity of the pores (e.g., a measure oflength to diameter of the paths through the pores) can be important inevaluating the probable success of such a coating in use on a prostheticdevice. See, also, U.S. Pat. No. 4,213,816 to Morris issued Jul. 22,1980. The porous coating can be applied in the form of a powder and thearticle as a whole subjected to an elevated temperature that bonds thepowder to the substrate. Selection of suitable polymers and/or powdercoatings can be determined in view of the teachings and references citedherein, for example based on the melt index of each.

B. Biological Repair Material

Repair materials can also include one or more biological material eitheralone or in combination with non-biological materials. For example, anybase material can be designed or shaped and suitable cartilagereplacement or regenerating material(s) such as fetal cartilage cellscan be applied to be the base. The cells can be then be grown inconjunction with the base until the thickness (and/or curvature) of thecartilage surrounding the cartilage defect has been reached. Conditionsfor growing cells (e.g., chondrocytes) on various substrates in culture,ex vivo and in vivo are described, for example, in U.S. Pat. No.5,478,739 to Slivka et al. issued Dec. 26, 1995; U.S. Pat. No. 5,842,477to Naughton et al. issued Dec. 1, 1998; U.S. Pat. No. 6,283,980 toVibe-Hansen et al., issued Sep. 4, 2001, and U.S. Pat. No. 6,365,405 toSalzmann et al. issued Apr. 2, 2002. Non-limiting examples of suitablesubstrates include plastic, tissue scaffold, a bone replacement material(e.g., a hydroxyapatite, a bioresorbable material), or any othermaterial suitable for growing a cartilage replacement or regeneratingmaterial on it.

Biological polymers can be naturally occurring or produced in vitro byfermentation and the like. Suitable biological polymers include, withoutlimitation, collagen, elastin, silk, keratin, gelatin, polyamino acids,cat gut sutures, polysaccharides (e.g., cellulose and starch) andmixtures thereof. Biological polymers can be bioresorbable.

Biological materials used in the methods described herein can beautografts (from the same subject); allografts (from another individualof the same species) and/or xenografts (from another species). See,also, International Patent Publications WO 02/22014 to Alexander et al.published Mar. 21, 2002 and WO 97/27885 to Lee published Aug. 7, 1997.In certain embodiments autologous materials are preferred, as they cancarry a reduced risk of immunological complications to the host,including re-absorption of the materials, inflammation and/or scarringof the tissues surrounding the implant site.

In one embodiment of the invention, a probe is used to harvest tissuefrom a donor site and to prepare a recipient site. The donor site can belocated in a xenograft, an allograft or an autograft. The probe is usedto achieve a good anatomic match between the donor tissue sample and therecipient site. The probe is specifically designed to achieve a seamlessor near seamless match between the donor tissue sample and the recipientsite. The probe can, for example, be cylindrical. The distal end of theprobe is typically sharp in order to facilitate tissue penetration.Additionally, the distal end of the probe is typically hollow in orderto accept the tissue. The probe can have an edge at a defined distancefrom its distal end, e.g. at 1 cm distance from the distal end and theedge can be used to achieve a defined depth of tissue penetration forharvesting. The edge can be external or can be inside the hollow portionof the probe. For example, an orthopedic surgeon can take the probe andadvance it with physical pressure into the cartilage, the subchondralbone and the underlying marrow in the case of a joint such as a kneejoint. The surgeon can advance the probe until the external or internaledge reaches the cartilage surface. At that point, the edge will preventfurther tissue penetration thereby achieving a constant and reproducibletissue penetration. The distal end of the probe can include one or moreblades, saw-like structures, or tissue cutting mechanism. For example,the distal end of the probe can include an iris-like mechanismconsisting of several small blades. The blade or blades can be movedusing a manual, motorized or electrical mechanism thereby cuttingthrough the tissue and separating the tissue sample from the underlyingtissue. Typically, this will be repeated in the donor and the recipient.In the case of an iris-shaped blade mechanism, the individual blades canbe moved so as to close the iris thereby separating the tissue samplefrom the donor site.

In another embodiment of the invention, a laser device or aradiofrequency device can be integrated inside the distal end of theprobe. The laser device or the radiofrequency device can be used to cutthrough the tissue and to separate the tissue sample from the underlyingtissue.

In one embodiment of the invention, the same probe can be used in thedonor and in the recipient. In another embodiment, similarly shapedprobes of slightly different physical dimensions can be used. Forexample, the probe used in the recipient can be slightly smaller thanthat used in the donor thereby achieving a tight fit between the tissuesample or tissue transplant and the recipient site. The probe used inthe recipient can also be slightly shorter than that used in the donorthereby correcting for any tissue lost during the separation or cuttingof the tissue sample from the underlying tissue in the donor material.

Any biological repair material can be sterilized to inactivatebiological contaminants such as bacteria, viruses, yeasts, molds,mycoplasmas and parasites. Sterilization can be performed using anysuitable technique, for example radiation, such as gamma radiation.

Any of the biological materials described herein can be harvested withuse of a robotic device. The robotic device can use information from anelectronic image for tissue harvesting.

In certain embodiments, the cartilage replacement material has aparticular biochemical composition. For instance, the biochemicalcomposition of the cartilage surrounding a defect can be assessed bytaking tissue samples and chemical analysis or by imaging techniques.For example, WO 02/22014 to Alexander describes the use of gadoliniumfor imaging of articular cartilage to monitor glycosaminoglycan contentwithin the cartilage. The cartilage replacement or regenerating materialcan then be made or cultured in a manner, to achieve a biochemicalcomposition similar to that of the cartilage surrounding theimplantation site. The culture conditions used to achieve the desiredbiochemical compositions can include, for example, varyingconcentrations. Biochemical composition of the cartilage replacement orregenerating material can, for example, be influenced by controllingconcentrations and exposure times of certain nutrients and growthfactors.

III. Devices Design

A. Cartilage Models

Using information on thickness and curvature of the cartilage, aphysical model of the surfaces of the articular cartilage and of theunderlying bone can be created. This physical model can berepresentative of a limited area within the joint or it can encompassthe entire joint. For example, in the knee joint, the physical model canencompass only the medial or lateral femoral condyle, both femoralcondyles and the notch region, the medial tibial plateau, the lateraltibial plateau, the entire tibial plateau, the medial patella, thelateral patella, the entire patella or the entire joint. The location ofa diseased area of cartilage can be determined, for example using a 3Dcoordinate system or a 3D Euclidian distance as described in WO02/22014.

In this way, the size of the defect to be repaired can be determined. Aswill be apparent, some, but not all, defects will include less than theentire cartilage. Thus, in one embodiment of the invention, thethickness of the normal or only mildly diseased cartilage surroundingone or more cartilage defects is measured. This thickness measurementcan be obtained at a single point or, preferably, at multiple points,for example 2 point, 4-6 points, 7-10 points, more than 10 points orover the length of the entire remaining cartilage. Furthermore, once thesize of the defect is determined, an appropriate therapy (e.g.,articular repair system) can be selected such that as much as possibleof the healthy, surrounding tissue is preserved.

In other embodiments, the curvature of the articular surface can bemeasured to design and/or shape the repair material. Further, both thethickness of the remaining cartilage and the curvature of the articularsurface can be measured to design and/or shape the repair material.Alternatively, the curvature of the subchondral bone can be measured andthe resultant measurement(s) can be used to either select or shape acartilage replacement material. For example, the contour of thesubchondral bone can be used to re-create a virtual cartilage surface:the margins of an area of diseased cartilage can be identified. Thesubchondral bone shape in the diseased areas can be measured. A virtualcontour can then be created by copying the subchondral bone surface intothe cartilage surface, whereby the copy of the subchondral bone surfaceconnects the margins of the area of diseased cartilage.

Turning now to FIGS. 7A-H, various stages of knee resurfacing steps areshown. FIG. 7A illustrates an example of normal thickness cartilage 700in the anterior, central and posterior portion of a femoral condyle 702with a cartilage defect 705 in the posterior portion of the femoralcondyle. FIG. 7B shows the detection of a sudden change in thicknessindicating the margins of a cartilage defect 710 that would be observedusing the imaging techniques or the mechanical, optical, laser orultrasound techniques described above. FIG. 7C shows the margins of aweight-bearing surface 715 mapped onto the articular cartilage 700.Cartilage defect 705 is located within the weight-bearing surface 715.

FIG. 7D shows an intended implantation site (stippled line) 720 andcartilage defect 705. In this depiction, the implantation site 720 isslightly larger than the area of diseased cartilage 705. FIG. 7E depictsplacement of a single component articular surface repair system 725. Theexternal surface of the articular surface repair system 726 has acurvature that seamlessly extends from the surrounding cartilage 700resulting in good postoperative alignment between the surrounding normalcartilage 700 and the articular surface repair system 725.

FIG. 7F shows an exemplary multi-component articular surface repairsystem 730. The distal surface 733 of the second component 732 has acurvature that extends from that of the adjacent subchondral bone 735.The first component 736 has a thickness t and surface curvature 738 thatextends from the surrounding normal cartilage 700. In this embodiment,the second component 732 could be formed from a material with a Shore orRockwell hardness that is greater than the material forming the firstcomponent 736, if desired. Thus it is contemplated that the secondcomponent 732 having at least portion of the component in communicationwith the bone of the joint is harder than the first component 736 whichextends from the typically naturally softer cartilage material. Otherconfigurations, of course, are possible without departing from the scopeof the invention.

By providing a softer first component 736 and a firmer second component732, the overall implant can be configured so that its relative hardnessis analogous to that of the bone-cartilage or bone-meniscus area that itabuts. Thus, the softer material first component 736, being formed of asofter material, could perform the cushioning function of the nearbymeniscus or cartilage.

FIG. 7G shows another single component articular surface repair system740 with a peripheral margin 745 which is configured so that it issubstantially non-perpendicular to the surrounding or adjacent normalcartilage 700. FIG. 7H shows a multi-component articular surface repairsystem 750 with a first component 751 and a second component 752 similarto that shown in FIG. 7G with a peripheral margin 745 of the secondcomponent 745 substantially non-perpendicular to the surrounding oradjacent normal cartilage 700.

Now turning to FIGS. 8A-E, these figures depict exemplary knee imagingand resurfacing processes. FIG. 8A depicts a magnified view of an areaof diseased cartilage 805 demonstrating decreased cartilage thicknesswhen compared to the surrounding normal cartilage 800. The margins 810of the defect have been determined. FIG. 8B depicts the measurement ofcartilage thickness 815 adjacent to the defect 805. FIG. 8C depicts theplacement of a multi-component mini-prosthesis 824 for articularresurfacing. The thickness 820 of the first component 823 closelyapproximates that of the adjacent normal cartilage 800. The thicknesscan vary in different regions of the prosthesis. The curvature of thedistal portion 824 of the first component 823 closely approximates anextension of the normal cartilage 800 surrounding the defect. Thecurvature of the distal portion 826 of the second component 825 is aprojection of the surface 827 of the adjacent subchondral bone 830 andcan have a curvature that is the same, or substantially similar, to allor part of the surrounding subchondral bone.

FIG. 8D is a schematic depicting placement of a single componentmini-prosthesis 840 utilizing anchoring stems 845. As will beappreciated by those of skill in the art, a variety of configurations,including stems, posts, and nubs can be employed. Additionally, thecomponent is depicted such that its internal surface 829 is locatedwithin the subchondral bone 830. In an alternative construction, theinterior surface 829 conforms to the surface of the subchondral bone831.

FIG. 8E depicts placement of a single component mini-prosthesis 840utilizing anchoring stems 845 and an opening at the external surface 850for injection of bone cement 855 or other suitable material. Theinjection material 855 can freely extravasate into the adjacent bone andmarrow space from several openings at the undersurface of themini-prosthesis 860 thereby anchoring the mini-prosthesis.

FIGS. 9A-C, depict an alternative knee resurfacing device. FIG. 9Adepicts a normal thickness cartilage in the anterior, central andposterior portion of a femoral condyle 900 and a large area of diseasedcartilage 905 toward the posterior portion of the femoral condyle. FIG.9B depicts placement of a single component articular surface repairsystem 910. Again, the implantation site has been prepared with a singlecut 921, as illustrated. However, as will be appreciated by those ofskill in the art, the repair system can be perpendicular to the adjacentnormal cartilage 900 without departing from the scope of the invention.The articular surface repair system is not perpendicular to the adjacentnormal cartilage 900. FIG. 9C depicts a multi-component articularsurface repair system 920. Again, the implantation site has beenprepared with a single cut (cut line shown as 921). The second component930 has a curvature similar to the extended surface 930 adjacentsubchondral bone 935. The first component 940 has a curvature thatextends from the adjacent cartilage 900.

B. Device Modeling In Situ

Another approach to repairing a defect is to model defect repair systemin situ, as shown in FIGS. 10A-B. As shown in FIG. 10A, one approachwould be to insert a hollow device, such as a balloon, into the targetjoint 1000. Any device capable of accepting, for example, injections ofmaterial would be suitable. Suitable injection materials include, forexample, polymers and other materials discussed in Section II, above,can be used without departing from the scope of the invention.

In one embodiment it is contemplated that an insertion device has asubstantially fixed shape that matches at least one articular surface orsubchondral bone of the joint. After inserting the insertion device1000, material is injected into the joint through the insertion device1010 where it then hardens in situ, forming an implant 1052. Theinjection material can optionally bond to the device while hardening.

Alternatively, the implant can be removed after hardening 1020 forfurther processing 1030, such as polishing, e.g. as described SectionIV.

Where the implant is removable after hardening in situ, it can bepreferable to have the implant be formed so that it is collapsible,foldable or generally changeable in shape to facilitate removal. Afterprocessing, the implant can be reinstalled 1040.

One or more molds can be applied to one or more articular surfaces. Themold can have an internal surface facing the articular surface thatsubstantially conforms to the shape of the articular cartilage and/orthe shape of the subchondral bone. A hardening material including apolymer or metals can then be injected through an opening in the mold.The opening can include a membrane that allows insertion of an injectiondevice such as a needle. The membrane helps to avoid reflux of theinjected material into the joint cavity. Alternatively, the mold can bemade of a material that provides sufficient structural rigidity to allowhardening of the injected substance with the proper shape while allowingfor placement of needles and other devices through the mold.

Additionally, the implant device can be composed of a plurality ofsubcomponents, where the volume or size of each of the subcomponents issmaller than the volume of the implant. The different subcomponents canbe connected or assembled prior to insertion into the joint 1050(whether outside the body or adjacent the joint but within orsubstantially within the body), or, in some instances, can be assembledafter insertion to the joint 1052. The subcomponents can be disassembledinside the joint, or adjacent the joint, once hardening of theinjectable material has occurred.

Additionally, the implant can be fixed to the surface of the bone afterimplantation 1060 For example, fixation mechanisms can includemechanical structures such as fins, keels, teeth and pegs ornon-mechanical means, such as bone cement, etc. Typically after thedevice is implanted and/or fixed within the joint, the functionality ofthe implant is tested 1070 to determine whether it enables the joint toengage in a desired range of motion. As will be appreciated by those ofskill in the art, one or more of these steps can be repeated withoutdeparting from the scope of the invention, as shown by the optionalrepeat steps 1001, 1011, 1021, 1031, 1041, 1051, 1053, 1061 and 1071.

As shown in FIG. 10B, another approach would be to insert a retainingdevice into the target joint 1002. Any device capable of accepting, forexample, injections of material would be suitable. Suitable materialsinclude, for example, polymers and other materials discussed in SectionII, above, can be used without departing from the scope of theinvention.

In one embodiment it is contemplated that an insertion device has asubstantially fixed shape that matches at least one articular surface orsubchondral bone of the joint. After inserting the retaining device1002, material is injected into a hollow area formed between theretaining device and the joint surface through an aperture 1012 where itthen hardens in situ, forming an implant 1052. The injection materialcan optionally bond to the device while hardening.

Alternatively, the implant can be removed after hardening 1020 forfurther processing 1030, such as polishing, e.g. as described SectionIV.

Where the implant is removable after hardening in situ, it can bepreferable to have the implant be formed so that it is collapsible,foldable or generally changeable in shape to facilitate removal. Afterprocessing, the implant can be reinstalled 1040.

Additionally, the implant device can be composed of a plurality ofsubcomponents, where the volume or size of each of the subcomponents issmaller than the volume of the implant. The different subcomponents canbe connected or assembled prior to insertion into the joint 1050(whether outside the body or adjacent the joint but within orsubstantially within the body), or, in some instances, can be assembledafter insertion to the joint 1052. The subcomponents can be disassembledinside the joint, or adjacent the joint, once hardening of theinjectable material has occurred.

Additionally, the implant can be fixed to the surface of the bone afterimplantation 1060 For example, fixation mechanisms can includemechanical structures such as fins, keels, teeth and pegs ornon-mechanical means, such as bone cement, etc. Typically after thedevice is implanted and/or fixed within the joint, the functionality ofthe implant is tested 1070 to determine whether it enables the joint toengage in a desired range of motion. As will be appreciated by those ofskill in the art, one or more of these steps can be repeated withoutdeparting from the scope of the invention, as shown by the optionalrepeat steps 1003, 1013, 1021, 1031, 1041, 1051, 1053, 1061 and 1071.

Prior to performing the method shown in FIG. 10B, one or more holes orapertures can be drilled into the surface of the bone at an angle eitherperpendicular to the bone surface or set at an angle. Upon injectingmaterial underneath the retaining device, the material embeds within theholes and form pegs upon hardening.

In one contemplated embodiment, at least a portion of the implantationdevice remains in situ after hardening of the injection material. Inthis scenario, the implantation device can be formed from abio-resorbable material. In this instance, the container forming theimplantation device can be resorbed, typically some time after hardeningof the injection material.

The shape of the implantation device can be fixed. Where the shape isfixed, an imaging test or intraoperative measurement can be used toeither shape or select the best fitting device for a particular patient,for example, using the imaging techniques and intraoperative measurementtechniques described in SECTIONS IA-B, above.

In other embodiments, portions of the device can be rigid, orsubstantially rigid, while other portions of the device are deformableor malleable. Alternatively, a portion of the device can be relativelymore rigid than another portion, without any requirement that anysection be rigid, deformable or malleable, but that sections vary inhardness relative to another section. In this manner the shape of therigid, substantially rigid, or relatively more rigid section can bedetermined, for example, using an imaging test. In contrast, it ispossible that the malleable, deformable, or relatively more deformableportion of the implantation device can then take the shape of one ormore articular surface in situ. This occurs particularly after theimplantation material has been injected and while the material ishardening in situ. In still other embodiments, the entire device can bedeformable.

In other embodiments, the implantation device can be expandable orcollapsible. For example, a support structure such as a Nitinol™ meshcan be inserted into the joint. Insertion can occur via, for example, acatheter or an arthroscopy portal. Once inside the joint, theimplantation device can then be expanded. The implantation device caninclude a receptacle, such as a bag, to receive the injection ofhardening material, such as polyethylene or other liquid including metalpreparations. The receptacle portion of the implantation device can bebio-resorbable and/or can bond with the injected material.Alternatively, the implantation device can be removed subsequent toinjecting the material. Where a supporting material is used, thesupporting material can be removed concurrently or subsequent to theremoval of the implantation device, either via an incision or bycollapsing the implantation device and removing it via, for example, thecatheter or arthroscopy portal.

In another embodiment, a balloon such as that shown in FIGS. 11A-E, canbe used as the implantation device. Different balloon shapes and sizescan be made available. A detailed description of all possible shapes andsizes for the balloons is not included to avoid obscuring the invention,but would be apparent to those of skill in the art. Where a balloon isused, it can be inserted into a joint and inflated. The size, height,shape and position of the balloon can be evaluated arthroscopically orvia an open incision or using, for example, an imaging test relative tothe articular surface and the other articular strictures. Range ofmotion testing can be performed in order to ensure adequate size, shapeand position of the device during the full range of motion.

After insertion, the balloon can be slowly injected with, for example, aself-hardening material, or material that hardens upon activation.Suitable materials are described below and would be apparent to those ofskill in the art. Typically, upon injection, the material is in a fluidor semi-fluid state. The material expands the balloon as it is injectedwhich results in the balloon taking on the shape of the articularsurface, for example as shown in FIG. 11A, and other articularstructures such that it fills the defect.

The balloon can be slowly injected with a self hardening or hardeningmaterial such as a polymer and even metals. The material is initially ina fluid or semi-fluid state. The material expands the balloon wherebythe shape of the balloon will take substantially the shape of thearticular surface(s) and other articular structures. The polymer willsubsequently harden inside the balloon thereby substantially taking theshape of the articular cavity and articular surface(s)/structures. Theballoon can also be composed of a bio-resorbable material. The ballooncan also be removed after the procedure.

Comparing, for example, the embodiments illustrated in FIGS. 11A-C, FIG.11A illustrates a single balloon 1100 inserted between two jointsurfaces 1102, 1104 of a joint 1110. In this figure, the joint surfacesare illustrated with associated cartilage 1106, 1108. The proximal end1112 of the balloon is configured to communicate with a device thatenables the balloon to be inflated, e.g. by filling the balloon 1100with a substance. Substances include, but are not limited to, air,polymers, crystal free metals, or any other suitable material, such asthose discussed in Section II above. The balloon 1100 of FIG. 11A isconfigured such that the distal end of the balloon 1114 does not extendbeyond distal end of the joint 1120 (where the distal end of the jointis defined relative to the area of the joint where the balloon enteredthe joint).

FIG. 11B illustrates an alternative balloon 1130 wherein the distal end1114 of the balloon 1130 and the proximal end 1113 of the balloon 1130extends beyond the distal 1120 and proximal 1122 end of the joint. Thisextension can be optimized for flexion and extension by using differentballoon sizes. FIG. 11C illustrates a balloon 1140 wherein the balloon1140 is configured such that the distal end 1114 of the balloon 1140extends beyond the distal 1120 of the joint while the proximal end 1114of the balloon 1140 does not extend beyond the end of the joint. As willbe appreciated by those of skill in the art, other permutations arepossible without departing from the scope of the invention.

Additionally, a sharp instrument such as a scalpel can be inserted intothe balloon or adjacent to the balloon and the balloon can be cut orslit. The balloon can then be pulled back from the hardened material andremoved from the joint, preferably through a catheter or an arthroscopyportal.

More than one balloon can be used as illustrated in FIGS. 11D-G. Where aplurality of balloons used, the balloons can be configured such that theballoons are inserted side-by-side as shown by 1150, 1152 in FIG. 11D,inserted in different compartments as shown by 1154, 1156 in FIG. 11E,one or more balloons are encompassed within the lumen of anotherballoon, as shown by 1160, 1162 and 1170, 1172, 1174 in FIGS. 11F-G, ina top-bottom relationship, and/or combinations thereof.

Each balloon can have the same or different wall thickness or can becomposed of the same or different materials. As a result of differencesin material, a person of skill in the art will appreciate that theamount of pressure required to expand each of the balloons can varyeither uniformly or in a non-uniform fashion. These pressures would beknown to a person of skill in the art and are not discussed at lengthherein to avoid obscuring the invention.

For example, in one scenario the superior and inferior surface of afirst, inner balloon, can have a low inflation pressure relative to asecond balloon. Thus, as the material is injected, the pressure createdinside the lumen of the balloon is directly transmitted to one or morearticular surface. In this manner, the distance between the twoarticular surfaces can be controlled and a minimum distance can beobtained ensuring a sufficient thickness of the resultant implant. Thisembodiment can be useful in areas within or bordering the contact zoneof the articular surface.

A second outer or peripheral balloon can be provided that requires ahigher inflation pressure relative to the first balloon. The inner, lowinflation pressure balloon can be placed in the weight-bearing zone. Thesame balloon can also have different wall properties in differentregions of the balloon, e.g. a rigid wall with high inflation pressuresin the periphery and a less rigid wall with intermediate or lowinflation pressures in the center.

Alternatively, a first balloon, having a low inflation pressure relativeto a second balloon is provided in an area bordering the contact zone ofthe articular surface. Again, as material is injected, the pressurecreated inside the lumen of the balloon is directly transmitted to oneor more articular surface. In this manner, the distance between the twoarticular surfaces can be controlled and a minimum distance can beobtained ensuring a sufficient thickness of the resultant implant.

A second balloon can be provided at an area where there is relativelymore weight bearing. This balloon can be configured to require a higherinflation pressure relative to the first balloon.

Differences in wall thickness, pressure tolerances and expandability ofballoons can also be used to influence the resulting shape of theinjected material.

The results of using inflation devices, or balloons, with differing wallthicknesses or pressure tolerances is shown in FIGS. 12A-F. As shown inFIG. 12A the balloon 1200 has an upper surface 1210 and a lower surface1212 along with a proximal end 1214 and a distal end 1216. The relativepressure tolerance of the balloon or inflation device 1200 is lower onthe lower surface 1212 than the upper surface 1210. As a result, theupper surface of the balloon 1210 has a relatively flat configurationrelative to its corresponding joint surface while the lower surface 1212has a relatively conforming shape relative to its corresponding jointsurface.

Turning now to FIG. 12B, the inflation device used 1220 has a relativelyconstant pressure tolerance that is relatively high which results inboth the upper surface 1210 and the lower surface 1212 having relativelyflat configurations relative to each of its corresponding jointsurfaces, regardless of the joint surface anatomy.

FIG. 12C illustrates a balloon 1230 having a low inflation pressure atits proximal 1214 and distal 1216 ends, with a higher inflation pressureat a central region 1218. The result of this configuration is that whenthe balloon is inflated, the proximal and distal ends inflate to agreater profile (e.g., height) than the central region. The inflationpressure of the central region, although higher than the proximal anddistal ends, can be set such that the central region has a relativelyflat configuration relative to the corresponding joint surfaces, asshown, or can be configured to achieve the result shown in FIG. 12A.

As will be appreciated by those of skill in the art, any of theseballoons can be configured to have varying properties resulting inportions of the wall being less rigid than other portions, within thesame balloon, e.g. a rigid wall with high inflation pressures in theperiphery and a less rigid wall with intermediate or low inflationpressures in the center. Where there is more than one thickness to theballoon, it could, for example, have less stiffness anteriorly; greaterstiffness centrally, and less stiffness posteriorly. The wall thicknessvariability will enable the device to accommodate shape formation.Central thickness will help prevent the device from fully conforming tothe irregular surface of the joint, which may be important where thereare irregularities to the joint surface, such as bone spurs.Alternatively, if the central portion is of less stiffness than theanterior and posterior sections, the device would be configured toconform more closely to the shape of the joint surface, including anyirregularities. The closer the device conforms to the joint shape, themore the device seats within the joint.

Optionally, the surgeon can elect to remove surface irregularities,including bone spurs. This can be done using known techniques such asarthroscopy or open arthrotomy.

Where more than one balloon is used, the different balloons can havedifferent shapes and sizes. Shape and size can be adjusted or selectedfor a given patient and joint. In addition to size and shape differencesof the balloons, each of the balloons can also be configured to havedifferent and/or varying wall thicknesses. For example, one ballooncould be configured with a central portion that is less stiff than theanterior and posterior sections while a second balloon could beconfigured so that the central portion is of greater stiffness than theanterior and posterior section.

FIGS. 12D-E illustrate configurations using two balloons. As shown inFIG. 12D the first balloon 1244 sits within a second balloon 1242 toform an inflation device 1240. In this embodiment, the inferior surface1246 of the external second balloon 1242 is configured with an inflationpressure that enables at least one surface of the device to conform, orsubstantially conform, to the corresponding joint surface. FIG. 12E alsoillustrates a two balloon configuration 1250 with a first balloon 1254and a second balloon 1252. In this embodiment, the inflation pressure ofthe device is configured such that the surface does not substantiallyconform to the corresponding joint surface.

FIGS. 13A-J(1-3) illustrate a variety of cross-sections possible for theembodiments shown in FIGS. 11-12. These embodiments illustrate possibleprofiles achieved with a single balloon (FIGS. 13A(1-3)); a dual balloonembodiment wherein one balloon fits within a second balloon inapproximately a central position (FIG. 13B(1-3)) or in an off-centeredposition within a second balloon (FIGS. 13D(1-3)); a tri-balloon set-upwhere two balloons fit within a first balloon (FIGS. 13C(1-3)), threeballoons are positioned next to each other (FIGS. 13 H(1-3)), or twoballoons are adjacent each other while one balloon has another balloonwithin its lumen (FIGS. 13E(2-3), F(2), G(2)); a four balloon set-upwhere two balloons are adjacent each other and each one has a balloonwithin its lumen (FIG. 13G(3)) or three balloons are adjacent each otherwith at least one of the three balloons having another balloon withinits lumen (FIGS. 13I(2-3)), or a five balloon set up where threeballoons are positioned adjacent each other and two of the threeballoons have balloons within its lumen (FIG. 13J(1)). As will beappreciated by those of skill in the art, other combinations andprofiles are achievable using the teachings of the invention withoutdeparting from the scope of the invention. All possible combinationshave not been illustrated in order to avoid obscuring the invention.

In another embodiment, a probe can be inserted into the balloon or thedevice. The probe can be utilized for measuring the device thickness(e.g. minima and maxima). In this and other embodiments, the balloon canbe initially injected with a test material that is typically nothardening. Once inside the balloon or the device, the thickness of thedevice or the balloon can be measured, e.g. for a given inflationpressure. In this manner, a sufficient minimum implant thickness can beensured. Probes to measure the thickness of the device or the ballooninclude, but are not limited to ultrasound, including A-, B- or C-scan.

Turning now to FIGS. 14A-J which illustrate the cartilage repair systemdescribed in FIG. 10B utilizing the retaining device. FIGS. 14A and Dillustrate a cartilage defect 1501 on an articular surface 1500 in thesagittal plane S and the coronal plane C. The surgeon debrides thedefect thereby optionally creating smooth margins 1502.

A retaining device 1510 is applied to the defect 1501 to define a cavity1520. A hardening material can be injected into an aperture 1512 in theretaining device 1510. Suitable materials include, but not limited to, apolymer or a crystal free metal. Additionally, as will be appreciated bythose of skill in the art, the material injected can be initially inpowder form with a liquid catalyst or hardening material injectedthereafter.

As illustrated in FIG. 14G, the surface of the bone 1550 can beprepared, e.g. by curette or drill, so that the surface of the bone 1550defines small teeth, holes, or anchoring members, 1552 that help anchorthe resulting device to the articular surface 1550. As shown in FIGS.14G(2) and (5) the drill holes can be drilled parallel in relation toone another, where there are more than two, and perpendicular to thesurface of the subchondral bone 1552. Alternatively, the drill holes canbe drilled at an angle in relationship to each other and at a angle thatis not perpendicular to the subchondral bone 1553 as illustrated in FIG.15G(3-4). As will be appreciated by those of skill in the art, one ormore pegs can be created on the surface of the bone. For example FIG.14G(2) illustrates a two peg set-up while FIG. 14G(8) illustrates asingle peg scenario and FIG. 14G(4) illustrates a four peg scenariowhere some pegs are in parallel relationship while others are not. Asshown in FIG. 14G(9), the aperture (1552 or 1553) can be formed so thatthe bore does not form a cylinder, but rather has channel protrusions1572 into the bone that, when filled, form the turning channel for ascrew, thus resulting in the filled aperture forming a screw thatenables the anchored device to be removed by turning in a clockwise orcounter-clockwise direction.

As shown in FIG. 14H, a ridge 1546, typically circumferential, can beused. The circumferential ridge can help achieve a tight seal betweenthe detaining device and the cartilage in order to avoid spillage of theinjected material in the joint cavity. Alternatively, the periphery ofthe mold can include a soft, compressible material that helps achieve atight seal between the mold and the surrounding cartilage.

FIG. 14I illustrates the retaining mold with a handle placed on thesurface of a bone.

As shown in FIG. 14J, the retaining device 1510 can have one or morehandles 1547 attached to it. The handle can facilitate the surgeonmaintaining the retaining device in position while the injected materialhardens. The aperture 1512 of the retaining device accepts injectionsand can include a membrane 1513 as shown in FIG. 14J. The configurationassists in creating a tight seal after a needle 1560 or injectioninstrument used to inject the material 1570 into the cavity 1520 isremoved. Additionally, or in place of the membrane 1513, a cap 1514 canbe provided that seals the aperture 1512 after the material 1570 isinjected. Additionally, anchoring teeth 1590 can be provided thatcommunicate with the meniscus 1591 or cartilage surrounding a defect.The anchoring teeth 1590 help keep the device stable when placed overthe defect.

As illustrated in FIG. 14G(4) more than one aperture 1512, 1512′ can beprovided without departing from the scope of the invention.

The retaining device system can be designed to inject an area equal toor slightly greater than the area of diseased cartilage. Alternatively,the retaining device system can be designed for the entireweight-bearing surface or the entire articular surface of a compartment.Retaining devices can be used on opposing articular surfaces, e.g. on afemoral condyle and a tibial plateau, thereby recreating a smoothgliding surface on both articular surfaces.

The retaining device can be designed to allow for light exposureincluding UV light. For example, the retaining device can be made usinga transparent plastic. The retaining device can also be made to allowfor passage of ultrasound waves.

C. Customized Containers

In another embodiment of the invention, a container or well can beformed to the selected specifications, for example to match the materialneeded for a particular subject or to create a stock of repair materialsin a variety of sizes. The size and shape of the container can bedesigned using the thickness and curvature information obtained from thejoint and from the cartilage defect. More specifically, the inside ofthe container can be shaped to follow any selected measurements, forexample as obtained from the cartilage defect(s) of a particularsubject. The container can be filled with a cartilage replacement orregenerating material, for example, collagen-containing materials,plastics, bioresorbable materials and/or any suitable tissue scaffold.The cartilage regenerating or replacement material can also consist of asuspension of stem cells or fetal or immature or mature cartilage cellsthat subsequently develop to more mature cartilage inside the container.Further, development and/or differentiation can be enhanced with use ofcertain tissue nutrients and growth factors.

The material is allowed to harden and/or grow inside the container untilthe material has the desired traits, for example, thickness, elasticity,hardness, biochemical composition, etc. Molds can be generated using anysuitable technique, for example computer devices and automation, e.g.computer assisted design (CAD) and, for example, computer assistedmodeling (CAM). Because the resulting material generally follows thecontour of the inside of the container it will better fit the defectitself and facilitate integration.

D. Designs Encompassing Multiple Component Repair Materials

The articular repair system or implants described herein can include oneor more components.

FIGS. 15A-B shows single and multiple component devices. FIG. 15Aillustrates an example of a single component articular surface repairsystem 1400 with varying curvature and radii that fits within thesubchondral bone 1420 such that the interior surface 1402 of the system1400 does not form an extension of the surface of the subchondral bone1422. The articular surface repair system is chosen to include convex1402 and concave 1404 portions. Such devices can be preferable in alateral femoral condyle or small joints such as the elbow joint. FIG.15B depicts a multi-component articular surface repair system with asecond component 1410 with a surface 1412 that forms an extension of thesurface 1422 of the subchondral bone 1420 and a first component 1405with an interior surface 1406 that forms an extension of the curvatureand shape of the surrounding normal cartilage 1415. The second component1410 and the first component 1405 demonstrate varying curvatures andradii with convex and concave portions that correspond to the curvatureof the subchondral bone 1420 and/or the normal cartilage 1415. As willbe appreciated by those of skill in the art, these two components can beformed such that the parts are integrally formed with each other, or canbe formed such that each part abuts the other. Additionally, therelationship between the parts can be by any suitable mechanismincluding adhesives and mechanical means.

FIGS. 16A-B show articular repair systems 100 having an outer contour102 forming an extension of the surrounding normal cartilage 200. Thesystems are implanted into the underlying bone 300 using one or morepegs 150, 175. The pegs, pins, or screws can be porous-coated and canhave flanges 125 as shown in FIG. 15B.

FIG. 17 shows an exemplary articular repair device 500 including a flatsurface 510 to control depth and prevent toggle; an exterior surface 515having the contour of normal cartilage; flanges 517 to prevent rotationand control toggle; a groove 520 to facilitate tissue in-growth.

FIGS. 18A-D depict, in cross-section, another example of an implant 640with multiple anchoring pegs, stems, or screws 645. FIG. 18B-D showvarious cross-sectional representations of various possible embodimentsof the pegs, or anchoring stems. FIG. 18B shows a peg 645 having a notch646 or groove around its circumference; FIG. 18C shows a peg 645 withradially-extending arms 647 that help anchor the device in theunderlying bone; and FIG. 18D shows a peg 645 with multiple grooves orflanges 648.

FIGS. 19A-B depict an overhead view of an exemplary implant 650 withmultiple anchoring pegs 655 which illustrates that the pegs are notnecessarily linearly aligned along the longitudinal axis of the device.

FIG. 20A depicts an implant 660 with a peg 661 having radially extendingarms 665. FIGS. 20B-E are top views of the implant pegs illustrating avariety of suitable alternative shapes.

Examples of one-component systems include, but are not limited to, aplastic, a polymer, a metal, a metal alloy, crystal free metals, abiologic material or combinations thereof. In certain embodiments, thesurface of the repair system facing the underlying bone can be smooth.In other embodiments, the surface of the repair system facing theunderlying bone can be porous or porous-coated. In another aspect, thesurface of the repair system facing the underlying bone is designed withone or more grooves, for example to facilitate the in-growth of thesurrounding tissue. The external surface of the device can have astep-like design, which can be advantageous for altering biomechanicalstresses. Optionally, flanges can also be added at one or more positionson the device (e.g., to prevent the repair system from rotating, tocontrol toggle and/or prevent settling into the marrow cavity). Theflanges can be part of a conical or a cylindrical design. A portion orall of the repair system facing the underlying bone can also be flatwhich can help to control depth of the implant and to prevent toggle.

Non-limiting examples of multiple-component systems include combinationsof metal, plastic, metal alloys, crystal free metals, and one or morebiological materials. One or more components of the articular surfacerepair system can be composed of a biologic material (e.g. a tissuescaffold with cells such as cartilage cells or stem cells alone orseeded within a substrate such as a bioresorable material or a tissuescaffold, allograft, autograft or combinations thereof) and/or anon-biological material (e.g., polyethylene or a chromium alloy such aschromium cobalt).

Thus, the repair system can include one or more areas of a singlematerial or a combination of materials, for example, the articularsurface repair system can have a first and a second component. The firstcomponent is typically designed to have size, thickness and curvaturesimilar to that of the cartilage tissue lost while the second componentis typically designed to have a curvature similar to the subchondralbone. In addition, the first component can have biomechanical propertiessimilar to articular cartilage, including but not limited to similarelasticity and resistance to axial loading or shear forces. The firstand the second component can consist of two different metals or metalalloys. One or more components of the system (e.g., the second portion)can be composed of a biologic material including, but not limited tobone, or a non-biologic material including, but not limited tohydroxyapatite, tantalum, a chromium alloy, chromium cobalt or othermetal alloys.

One or more regions of the articular surface repair system (e.g., theouter margin of the first portion and/or the second portion) can bebioresorbable, for example to allow the interface between the articularsurface repair system and the patient's normal cartilage, over time, tobe filled in with hyaline or fibrocartilage. Similarly, one or moreregions (e.g., the outer margin of the first portion of the articularsurface repair system and/or the second portion) can be porous. Thedegree of porosity can change throughout the porous region, linearly ornon-linearly, for where the degree of porosity will typically decreasetowards the center of the articular surface repair system. The pores canbe designed for in-growth of cartilage cells, cartilage matrix, andconnective tissue thereby achieving a smooth interface between thearticular surface repair system and the surrounding cartilage.

The repair system (e.g., the second component in multiple componentsystems) can be attached to the patient's bone with use of a cement-likematerial such as methylmethacrylate, injectable hydroxy- orcalcium-apatite materials and the like.

In certain embodiments, one or more portions of the articular surfacerepair system can be pliable or liquid or deformable at the time ofimplantation and can harden later. Hardening can occur, for example,within 1 second to 2 hours (or any time period therebetween), preferablywith in 1 second to 30 minutes (or any time period therebetween), morepreferably between 1 second and 10 minutes (or any time periodtherebetween).

One or more components of the articular surface repair system can beadapted to receive injections. For example, the external surface of thearticular surface repair system can have one or more openings therein.The openings can be sized to receive screws, tubing, needles or otherdevices which can be inserted and advanced to the desired depth, forexample, through the articular surface repair system into the marrowspace. Injectables such as methylmethacrylate and injectable hydroxy- orcalcium-apatite materials can then be introduced through the opening (ortubing inserted therethrough) into the marrow space thereby bonding thearticular surface repair system with the marrow space. Similarly, screwsor pins, or other anchoring mechanisms. can be inserted into theopenings and advanced to the underlying subchondral bone and the bonemarrow or epiphysis to achieve fixation of the articular surface repairsystem to the bone. Portions or all components of the screw or pin canbe bioresorbable, for example, the distal portion of a screw thatprotrudes into the marrow space can be bioresorbable. During the initialperiod after the surgery, the screw can provide the primary fixation ofthe articular surface repair system. Subsequently, ingrowth of bone intoa porous coated area along the undersurface of the articular cartilagerepair system can take over as the primary stabilizer of the articularsurface repair system against the bone.

The articular surface repair system can be anchored to the patient'sbone with use of a pin or screw or other attachment mechanism. Theattachment mechanism can be bioresorbable. The screw or pin orattachment mechanism can be inserted and advanced towards the articularsurface repair system from a non-cartilage covered portion of the boneor from a non-weight-bearing surface of the joint.

The interface between the articular surface repair system and thesurrounding normal cartilage can be at an angle, for example oriented atan angle of 90 degrees relative to the underlying subchondral bone.Suitable angles can be determined in view of the teachings herein, andin certain cases, non-90 degree angles can have advantages with regardto load distribution along the interface between the articular surfacerepair system and the surrounding normal cartilage.

The interface between the articular surface repair system and thesurrounding normal cartilage and/or bone can be covered with apharmaceutical or bioactive agent, for example a material thatstimulates the biological integration of the repair system into thenormal cartilage and/or bone. The surface area of the interface can beirregular, for example, to increase exposure of the interface topharmaceutical or bioactive agents.

E. Pre-Existing Repair Systems

As described herein, repair systems, including surgical instruments,templates, guides and/or molds, of various sizes, curvatures andthicknesses can be obtained. These repair systems, including surgicalinstruments, guides, templates and/or molds, can be catalogued andstored to create a library of systems from which an appropriate systemfor an individual patient can then be selected. In other words, adefect, or an articular surface, is assessed in a particular subject anda pre-existing repair system, including surgical instruments, templates,guides and/or molds, having a suitable shape and size is selected fromthe library for further manipulation (e.g., shaping) and implantation.

F. Mini-Prosthesis

As noted above, the methods and compositions described herein can beused to replace only a portion of the articular surface, for example, anarea of diseased cartilage or lost cartilage on the articular surface.In these systems, the articular surface repair system can be designed toreplace only the area of diseased or lost cartilage or it can extendbeyond the area of diseased or lost cartilage, e.g., 3 or 5 mm intonormal adjacent cartilage. In certain embodiments, the prosthesisreplaces less than about 70% to 80% (or any value therebetween) of thearticular surface (e.g., any given articular surface such as a singlefemoral condyle, etc.), preferably, less than about 50% to 70% (or anyvalue therebetween), more preferably, less than about 30% to 50% (or anyvalue therebetween), more preferably less than about 20% to 30% (or anyvalue therebetween), even more preferably less than about 20% of thearticular surface.

The prosthesis can include multiple components, for example a componentthat is implanted into the bone (e.g., a metallic device) attached to acomponent that is shaped to cover the defect of the cartilage overlayingthe bone. Additional components, for example intermediate plates,meniscal repair systems and the like can also be included. It iscontemplated that each component replaces less than all of thecorresponding articular surface. However, each component need notreplace the same portion of the articular surface. In other words, theprosthesis can have a bone-implanted component that replaces less than30% of the bone and a cartilage component that replaces 60% of thecartilage. The prosthesis can include any combination, provided eachcomponent replaces less than the entire articular surface.

The articular surface repair system can be formed or selected so that itwill achieve a near anatomic fit or match with the surrounding oradjacent cartilage. Typically, the articular surface repair system isformed and/or selected so that its outer margin located at the externalsurface will be aligned with the surrounding or adjacent cartilage.

Thus, the articular repair system can be designed to replace theweight-bearing portion (or more or less than the weight bearing portion)of an articular surface, for example in a femoral condyle. Theweight-bearing surface refers to the contact area between two opposingarticular surfaces during activities of normal daily living (e.g.,normal gait). At least one or more weight-bearing portions can bereplaced in this manner, e.g., on a femoral condyle and on a tibia.

In other embodiments, an area of diseased cartilage or cartilage losscan be identified in a weight-bearing area and only a portion of theweight-bearing area, specifically the portion containing the diseasedcartilage or area of cartilage loss, can be replaced with an articularsurface repair system.

In another embodiment, the articular repair system can be designed orselected to replace substantially all of the articular surface, e.g. acondyle.

In another embodiment, for example, in patients with diffuse cartilageloss, the articular repair system can be designed to replace an areaslightly larger than the weight-bearing surface.

In certain aspects, the defect to be repaired is located only on onearticular surface, typically the most diseased surface. For example, ina patient with severe cartilage loss in the medial femoral condyle butless severe disease in the tibia, the articular surface repair systemcan only be applied to the medial femoral condyle. Preferably, in anymethods described herein, the articular surface repair system isdesigned to achieve an exact or a near anatomic fit with the adjacentnormal cartilage.

In other embodiments, more than one articular surface can be repaired.The area(s) of repair will be typically limited to areas of diseasedcartilage or cartilage loss or areas slightly greater than the area ofdiseased cartilage or cartilage loss within the weight-bearingsurface(s).

The implant and/or the implant site can be sculpted to achieve a nearanatomic alignment between the implant and the implant site. In anotherembodiment of the invention, an electronic image is used to measure thethickness, curvature, or shape of the articular cartilage or thesubchondral bone, and/or the size of a defect, and an articular surfacerepair system is selected using this information. The articular surfacerepair system can be inserted arthroscopically. The articular surfacerepair system can have a single radius. More typically, however, asshown in FIG. 15A, discussed above, the articular surface repair system1500 has varying curvatures and radii within the same plane, e.g.anteroposterior or mediolateral or superoinferior or oblique planes, orwithin multiple planes. In this manner, the articular surface repairsystem can be shaped to achieve a near anatomic alignment between theimplant and the implant site. This design allows not only allows fordifferent degrees of convexity or concavity, but also for concaveportions within a predominantly convex shape or vice versa 1500.

In another embodiment the articular surface repair system has ananchoring stem, used to anchor the device, for example, as described inU.S. Pat. No. 6,224,632 to Pappas et al issued May 1, 2001. The stem, orpeg, can have different shapes including conical, rectangular, fin amongothers. The mating bone cavity is typically similarly shaped as thecorresponding stem.

As shown in FIG. 16, discussed above, the articular surface repairsystem 100 can be affixed to the subchondral bone 300, with one or morestems, or pegs, 150 extending through the subchondral plate into themarrow space. In certain instances, this design can reduce thelikelihood that the implant will settle deeper into the joint over timeby resting portions of the implant against the subchondral bone. Thestems, or pegs, can be of any shape suitable to perform the function ofanchoring the device to the bone. For example, the pegs can becylindrical or conical. Optionally, the stems, or pegs, can furtherinclude notches or openings to allow bone in-growth. In addition, thestems can be porous coated for bone in-growth. The anchoring stems orpegs can be affixed to the bone using bone cement. An additionalanchoring device can also be affixed to the stem or peg. The anchoringdevice can have an umbrella shape (e.g., radially expanding elements)with the wider portion pointing towards the subchondral bone and awayfrom the peg. The anchoring device can be advantageous for providingimmediate fixation of the implant. The undersurface of the articularrepair system facing the subchondral bone can be textured or roughthereby increasing the contact surface between the articular repairsystem and the subchondral bone. Alternatively, the undersurface of thearticular repair system can be porous coated thereby allowing in-growth.The surgeon can support the in-growth of bone by treating thesubchondral bone with a rasp, typically to create a larger surface areaand/or until bleeding from the subchondral bone occurs.

In another embodiment, the articular surface repair system can beattached to the underlying bone or bone marrow using bone cement. Bonecement is typically made from an acrylic polymeric material. Typically,the bone cement is comprised of two components: a dry powder componentand a liquid component, which are subsequently mixed together. The drycomponent generally includes an acrylic polymer, such aspolymethylmethacrylate (PMMA). The dry component can also contain apolymerization initiator such as benzoylperoxide, which initiates thefree-radical polymerization process that occurs when the bone cement isformed. The liquid component, on the other hand, generally contains aliquid monomer such as methyl methacrylate (MMA). The liquid componentcan also contain an accelerator such as an amine (e.g.,N,N-dimethyl-p-toluidine). A stabilizer, such as hydroquinone, can alsobe added to the liquid component to prevent premature polymerization ofthe liquid monomer. When the liquid component is mixed with the drycomponent, the dry component begins to dissolve or swell in the liquidmonomer. The amine accelerator reacts with the initiator to form freeradicals that begin to link monomer units to form polymer chains. In thenext two to four minutes, the polymerization process proceeds changingthe viscosity of the mixture from a syrup-like consistency (lowviscosity) into a dough-like consistency (high viscosity). Ultimately,further polymerization and curing occur, causing the cement to hardenand affix a prosthesis to a bone.

In certain aspects of the invention, as shown in FIG. 7E, above, bonecement 755 or another liquid attachment material such as injectablecalciumhydroxyapatite can be injected into the marrow cavity through oneor more openings 750 in the prosthesis. These openings in the prosthesiscan extend from the articular surface to the undersurface of theprosthesis 760. After injection, the openings can be closed with apolymer, silicon, metal, metal alloy or bioresorbable plug.

In another embodiment, one or more components of the articular surfacerepair (e.g., the surface of the system that is pointing towards theunderlying bone or bone marrow) can be porous or porous coated. Avariety of different porous metal coatings have been proposed forenhancing fixation of a metallic prosthesis by bone tissue in-growth.Thus, for example, U.S. Pat. No. 3,855,638 to Pilliar issued Dec. 24,2974, discloses a surgical prosthetic device, which can be used as abone prosthesis, comprising a composite structure consisting of a solidmetallic material substrate and a porous coating of the same solidmetallic material adhered to and extending over at least a portion ofthe surface of the substrate. The porous coating consists of a pluralityof small discrete particles of metallic material bonded together attheir points of contact with each other to define a plurality ofconnected interstitial pores in the coating. The size and spacing of theparticles, which can be distributed in a plurality of monolayers, can besuch that the average interstitial pore size is not more than about 200microns. Additionally, the pore size distribution can be substantiallyuniform from the substrate-coating interface to the surface of thecoating. In another embodiment, the articular surface repair system cancontain one or more polymeric materials that can be loaded with andrelease therapeutic agents including drugs or other pharmacologicaltreatments that can be used for drug delivery. The polymeric materialscan, for example, be placed inside areas of porous coating. Thepolymeric materials can be used to release therapeutic drugs, e.g. boneor cartilage growth stimulating drugs. This embodiment can be combinedwith other embodiments, wherein portions of the articular surface repairsystem can be bioresorbable. For example, the first layer of anarticular surface repair system or portions of its first layer can bebioresorbable. As the first layer gets increasingly resorbed, localrelease of a cartilage growth-stimulating drug can facilitate in-growthof cartilage cells and matrix formation.

In any of the methods or compositions described herein, the articularsurface repair system can be pre-manufactured with a range of sizes,curvatures and thicknesses. Alternatively, the articular surface repairsystem can be custom-made for an individual patient.

IV. Manufacturing

A. Shaping

In certain instances shaping of the repair material will be requiredbefore or after formation (e.g., growth to desired thickness), forexample where the thickness of the required cartilage material is notuniform (e.g., where different sections of the cartilage replacement orregenerating material require different thicknesses).

The replacement material can be shaped by any suitable techniqueincluding, but not limited to, mechanical abrasion, laser abrasion orablation, radiofrequency treatment, cryoablation, variations in exposuretime and concentration of nutrients, enzymes or growth factors and anyother means suitable for influencing or changing cartilage thickness.See, e.g., WO 00/15153 to Mansmann published Mar. 23, 2000; If enzymaticdigestion is used, certain sections of the cartilage replacement orregenerating material can be exposed to higher doses of the enzyme orcan be exposed longer as a means of achieving different thicknesses andcurvatures of the cartilage replacement or regenerating material indifferent sections of said material.

The material can be shaped manually and/or automatically, for exampleusing a device into which a pre-selected thickness and/or curvature hasbeen input and then programming the device using the input informationto achieve the desired shape.

In addition to, or instead of, shaping the cartilage repair material,the site of implantation (e.g., bone surface, any cartilage materialremaining, etc.) can also be shaped by any suitable technique in orderto enhance integration of the repair material.

B. Sizing

The articular repair system can be formed or selected so that it willachieve a near anatomic fit or match with the surrounding or adjacentcartilage or subchondral bone or menisci and other tissue. The shape ofthe repair system can be based on the analysis of an electronic image(e.g. MRI, CT, digital tomosynthesis, optical coherence tomography orthe like). If the articular repair system is intended to replace an areaof diseased cartilage or lost cartilage, the near anatomic fit can beachieved using a method that provides a virtual reconstruction of theshape of healthy cartilage in an electronic image.

In one embodiment of the invention, a near normal cartilage surface atthe position of the cartilage defect can be reconstructed byinterpolating the healthy cartilage surface across the cartilage defector area of diseased cartilage. This can, for example, be achieved bydescribing the healthy cartilage by means of a parametric surface (e.g.a B-spline surface), for which the control points are placed such thatthe parametric surface follows the contour of the healthy cartilage andbridges the cartilage defect or area of diseased cartilage. Thecontinuity properties of the parametric surface will provide a smoothintegration of the part that bridges the cartilage defect or area ofdiseased cartilage with the contour of the surrounding healthycartilage. The part of the parametric surface over the area of thecartilage defect or area of diseased cartilage can be used to determinethe shape or part of the shape of the articular repair system to matchwith the surrounding cartilage.

In another embodiment, a near normal cartilage surface at the positionof the cartilage defect or area of diseased cartilage can bereconstructed using morphological image processing. In a first step, thecartilage can be extracted from the electronic image using manual,semi-automated and/or automated segmentation techniques (e.g., manualtracing, region growing, live wire, model-based segmentation), resultingin a binary image. Defects in the cartilage appear as indentations thatcan be filled with a morphological closing operation performed in 2-D or3-D with an appropriately selected structuring element. The closingoperation is typically defined as a dilation followed by an erosion. Adilation operator sets the current pixel in the output image to 1 if atleast one pixel of the structuring element lies inside a region in thesource image. An erosion operator sets the current pixel in the outputimage to 1 if the whole structuring element lies inside a region in thesource image. The filling of the cartilage defect or area of diseasedcartilage creates a new surface over the area of the cartilage defect orarea of diseased cartilage that can be used to determine the shape orpart of the shape of the articular repair system to match with thesurrounding cartilage or subchondral bone.

As described above, the articular repair system, including surgicaltools and instruments, molds, in situ repair systems, etc. can be formedor selected from a library or database of systems of various sizes,curvatures and thicknesses so that it will achieve a near anatomic fitor match with the surrounding or adjacent cartilage and/or subchondralbone. These systems can be pre-made or made to order for an individualpatient. In order to control the fit or match of the articular repairsystem with the surrounding or adjacent cartilage or subchondral bone ormenisci and other tissues preoperatively, a software program can be usedthat projects the articular repair system over the anatomic positionwhere it will be implanted. Suitable software is commercially availableand/or readily modified or designed by a skilled programmer.

In yet another embodiment, the articular repair system includingunicompartmental and total knee implants as well as hip devices can beprojected over the implantation site using one or more 2-D or 3-Dimages. The cartilage and/or subchondral bone and other anatomicstructures can be optionally extracted from a 2-D or 3-D electronicimage such as an MRI or a CT using manual, semi-automated and/orautomated segmentation techniques. A 2-D or 3-D representation of thecartilage and/or bone and other anatomic structures as well as thearticular repair system can be generated, for example using a polygon orNURBS surface or other parametric surface representation. Ligaments,menisci and other articular structures can be displayed in 2-D and 3-D.For a description of various parametric surface representations see, forexample Foley, J. D. et al., Computer Graphics Principles and Practicein C; Addison-Wesley, 2^(nd) edition, 1995).

The 2-D or 3-D representations of the cartilage and/or subchondral boneand other anatomic structures and the articular repair system can bemerged into a common coordinate system. The articular repair system,including surgical tools and instruments, molds, in situ repair systems,etc. can then be placed at the desired implantation site. Therepresentations of the cartilage, subchondral bone, ligaments, menisciand other anatomic structures and the articular repair system arerendered into a 2-D or 3-D image, for example application programminginterfaces (APIs) OpenGL® (standard library of advanced 3-D graphicsfunctions developed by SGI, Inc.; available as part of the drivers forPC-based video cards, for example from www.nvidia.com for NVIDIA videocards or www.3dlabs.com for 3Dlabs products, or as part of the systemsoftware for Unix workstations) or DirectX® (multimedia API forMicrosoft Windows® based PC systems; available from www.microsoft.com).The 2-D or 3-D image can be rendered or displayed showing the cartilage,subchondral bone, ligaments, menisci or other anatomic objects, and thearticular repair system from varying angles, e.g. by rotating or movingthem interactively or non-interactively, in real-time or non-real-time.

In another embodiment, the implantation site may be visualized using oneor more cross-sectional 2-D images, as described in U.S. Ser. No.10/305,652, entitled “Methods and Compositions for Articular Repair,”filed Nov. 27, 2002, which is hereby incorporated by reference in itsentirety. Typically, a series of 2-D cross-sectional images will beused. The 2-D images can be generated with imaging tests such as CT,MRI, digital tomosynthesis, ultrasound, optical imaging, opticalcoherence tomography, other imaging modalities using methods and toolsknown to those of skill in the art. The articular repair system orimplant can then be superimposed onto one or more of these 2-D images.The 2-D cross-sectional images may be reconstructed in other planes,e.g. from sagittal to coronal, etc. Isotropic data sets (e.g., data setswhere the slice thickness is the same or nearly the same as the in-planeresolution) or near isotropic data sets can also be used. Multipleplanes may be displayed simultaneously, for example using a split screendisplay. The operator may also scroll through the 2-D images in anydesired orientation in real time or near real time; the operator canrotate the imaged tissue volume while doing this. The articular repairsystem or implant may be displayed in cross-section utilizing differentdisplay planes, e.g. sagittal, coronal or axial, typically matchingthose of the 2-D images demonstrating the cartilage, subchondral bone,ligaments, menisci or other tissue. Alternatively, a three-dimensionaldisplay may be used for the articular repair system. The 2-D electronicimage and the 2-D or 3-D representation of the articular repair systemor implant may be merged into a common coordinate system. The cartilagerepair system or implant can then be placed at the desired implantationsite. The series of 2-D cross-sections of the anatomic structures, theimplantation site and the articular repair system or implant may bedisplayed interactively (e.g. the operator can scroll through a seriesof slices) or non-interactively (e.g. as an animation that moves throughthe series of slices), in real-time or non-real-time.

The software can be designed so that the articular repair system,including surgical tools and instruments, molds, in situ repair systems,etc. with the best fit relative to the cartilage and/or subchondral boneis automatically selected, for example using one or more of thetechniques described above. Alternatively, the operator can select anarticular repair system, including surgical tools and instruments,molds, in situ repair systems, etc. and project it or drag it onto theimplantation site displayed on the cross-sectional 2-D or the 3-Dimages. The operator can then move and rotate the articular repairsystem relative to the implantation site and scroll through across-sectional 2-D or 3-D display of the articular repair system and ofthe anatomic structures. The operator can perform a visual and/orcomputer-assisted inspection of the fit between the articular repairsystem and the implantation site. This can be performed for differentpositions of the joint, e.g. extension, 45, 90 degrees of flexion,adduction, abduction, internal or external rotation. The procedure canbe repeated until a satisfactory fit has been achieved. The procedurecan be entirely manual by the operator; it can, however, also becomputer-assisted. For example, the software can select a first trialimplant that the operator can test (e.g., evaluate the fit). Softwarethat highlights areas of poor alignment between the implant and thesurrounding cartilage or subchondral bone or menisci or other tissuescan also be designed and used. Based on this information, the softwareor the operator can select another implant and test its alignment.

In all of the above embodiments, the biomechanical axis and relevantanatomical axes or planes can be displayed simultaneous with the jointand/or articular repair device in the 2-D or 3-D display. Simultaneousdisplay of at least one or more biomechanical axes or anatomical axes orplanes can help improve the assessment of fit of the articular repairsystem. Biomechanical axis or relevant anatomical axes or planes canalso be displayed for different positions of the joint.

C. Rapid Prototyping, Other Manufacturing Techniques

Rapid protyping is a technique for fabricating a three-dimensionalobject from a computer model of the object. A special printer is used tofabricate the prototype from a plurality of two-dimensional layers.Computer software sections the representations of the object into aplurality of distinct two-dimensional layers and then athree-dimensional printer fabricates a layer of material for each layersectioned by the software. Together the various fabricated layers formthe desired prototype. More information about rapid prototypingtechniques is available in US Patent Publication No 2002/0079601A1 toRussell et al., published Jun. 27, 2002. An advantage to using rapidprototyping is that it enables the use of free form fabricationtechniques that use toxic or potent compounds safely. These compoundscan be safely incorporated in an excipient envelope, which reducesworker exposure

A powder piston and build bed are provided. Powder includes any material(metal, plastic, etc.) that can be made into a powder or bonded with aliquid. The power is rolled from a feeder source with a spreader onto asurface of a bed. The thickness of the layer is controlled by thecomputer. The print head then deposits a binder fluid onto the powderlayer at a location where it is desired that the powder bind. Powder isagain rolled into the build bed and the process is repeated, with thebinding fluid deposition being controlled at each layer to correspond tothe three-dimensional location of the device formation. For a furtherdiscussion of this process see, for example, US Patent Publication No2003/017365A1 to Monkhouse et al. published Sep. 18, 2003.

The rapid prototyping can use the two dimensional images obtained, asdescribed above in Section I, to determine each of the two-dimensionalshapes for each of the layers of the prototyping machine. In thisscenario, each two dimensional image slice would correspond to a twodimensional prototype slide. Alternatively, the three-dimensional shapeof the defect can be determined, as described above, and then brokendown into two dimensional slices for the rapid prototyping process. Theadvantage of using the three-dimensional model is that thetwo-dimensional slices used for the rapid prototyping machine can bealong the same plane as the two-dimensional images taken or along adifferent plane altogether.

Rapid prototyping can be combined or used in conjunction with castingtechniques. For example, a shell or container with inner dimensionscorresponding to an articular repair system including surgicalinstruments, molds, alignment guides or surgical guides, can be madeusing rapid prototyping. Plastic or wax-like materials are typicallyused for this purpose. The inside of the container can subsequently becoated, for example with a ceramic, for subsequent casting. Using thisprocess, personalized casts can be generated.

Rapid prototyping can be used for producing articular repair systemsincluding surgical tools, molds, alignment guides, cut guides etc. Rapidprototyping can be performed at a manufacturing facility. Alternatively,it may be performed in the operating room after an intraoperativemeasurement has been performed.

Alternatively, milling techniques can be utilized for producingarticular repair systems including surgical tools, molds, alignmentguides, cut guides etc.

Alternatively, laser based techniques can be utilized for producingarticular repair systems including surgical tools, molds, alignmentguides, cut guides etc.

V. Implantation

Following one or more manipulations (e.g., shaping, growth, development,etc), the cartilage replacement or regenerating material can then beimplanted into the area of the defect. Implantation can be performedwith the cartilage replacement or regenerating material still attachedto the base material or removed from the base material. Any suitablemethods and devices can be used for implantation, for example, devicesas described in U.S. Pat. No. 6,375,658 to Hangody et al. issued Apr.23, 2002; U.S. Pat. No. 6,358,253 to Torrie et al. issued Mar. 19, 2002;U.S. Pat. No. 6,328,765 to Hardwick et al. issued Dec. 11, 2001; andInternational Publication WO 01/19254 to Cummings et al. published Mar.22, 2001.

In selected cartilage defects, the implantation site can be preparedwith a single cut across the articular surface, for example, as shown inFIG. 8. In this case, single 810 and multi-component 820 prostheses canbe utilized.

A. The Joint Replacement Procedure

i. Knee Joint

Performing a total knee arthroplasty is a complicated procedure. Inreplacing the knee with an artificial knee, it is important to get theanatomical and mechanical axes of the lower extremity aligned correctlyto ensure optimal functioning of the implanted knee.

As shown in FIG. 21A, the center of the hip 1902 (located at the head1930 of the femur 1932), the center of the knee 1904 (located at thenotch where the intercondular tubercle 1934 of the tibia 1936 meet thefemur) and ankle 1906 lie approximately in a straight line 1910 whichdefines the mechanical axis of the lower extremity. The anatomic axis1920 aligns 5-7° offset θ from the mechanical axis in the valgus, oroutward, direction.

The long axis of the tibia 1936 is collinear with the mechanical axis ofthe lower extremity 1910. From a three-dimensional perspective, thelower extremity of the body ideally functions within a single planeknown as the median anterior-posterior plane (MAP-plane) throughout theflexion-extension arc. In order to accomplish this, the femoral head1930, the mechanical axis of the femur, the patellar groove, theintercondylar notch, the patellar articular crest, the tibia and theankle remain within the MAP-plane during the flexion-extension movement.During movement, the tibia rotates as the knee flexes and extends in theepicondylar axis which is perpendicular to the MAP-plane.

A variety of image slices can be taken at each individual joint, e.g.,the knee joint 1950-1950 _(n), and the hip joint 1952-1950 _(n). Theseimage slices can be used as described above in Section I along with animage of the full leg to ascertain the axis.

With disease and malfunction of the knee, alignment of the anatomic axisis altered. Performing a total knee arthroplasty is one solution forcorrecting a diseased knee. Implanting a total knee joint, such as thePFC Sigma RP Knee System by Johnson & Johnson, requires that a series ofresections be made to the surfaces forming the knee joint in order tofacilitate installation of the artificial knee. The resections should bemade to enable the installed artificial knee to achieveflexion-extension movement within the MAP-plane and to optimize thepatient's anatomical and mechanical axis of the lower extremity.

First, the tibia 1930 is resected to create a flat surface to accept thetibial component of the implant. In most cases, the tibial surface isresected perpendicular to the long axis of the tibia in the coronalplane, but is typically sloped 4-7° posteriorly in the sagittal plane tomatch the normal slope of the tibia. As will be appreciated by those ofskill in the art, the sagittal slope can be 0° where the device to beimplanted does not require a sloped tibial cut. The resection line 1958is perpendicular to the mechanical axis 1910, but the angle between theresection line and the surface plane of the plateau 1960 variesdepending on the amount of damage to the knee.

FIGS. 21B-D illustrate an anterior view of a resection of ananatomically normal tibial component, a tibial component in a varusknee, and a tibial component in a valgus knee, respectively. In eachfigure, the mechanical axis 1910 extends vertically through the bone andthe resection line 1958 is perpendicular to the mechanical axis 1910 inthe coronal plane, varying from the surface line formed by the jointdepending on the amount of damage to the joint. FIG. 21B illustrates anormal knee wherein the line corresponding to the surface of the joint1960 is parallel to the resection line 1958. FIG. 21C illustrates avarus knee wherein the line corresponding to the surface of the joint1960 is not parallel to the resection line 1958. FIG. 21D illustrates avalgus knee wherein the line corresponding to the surface of the joint1960 is not parallel to the resection line 1958.

Once the tibial surface has been prepared, the surgeon turns topreparing the femoral condyle.

The plateau of the femur 1970 is resected to provide flat surfaces thatcommunicate with the interior of the femoral prosthesis. The cuts madeto the femur are based on the overall height of the gap to be createdbetween the tibia and the femur. Typically, a 20 mm gap is desirable toprovide the implanted prosthesis adequate room to achieve full range ofmotion. The bone is resected at a 5-7° angle valgus to the mechanicalaxis of the femur. Resected surface 1972 forms a flat plane with anangular relationship to adjoining surfaces 1974, 1976. The angle θ′, θ″between the surfaces 1972-1974, and 1972-1976 varies according to thedesign of the implant.

ii. Hip Joint

As illustrated in FIG. 21F, the external geometry of the proximal femurincludes the head 1980, the neck 1982, the lesser trochanter 1984, thegreater trochanter 1986 and the proximal femoral diaphysis. The relativepositions of the trochanters 1984, 1986, the femoral head center 1902and the femoral shaft 1988 are correlated with the inclination of theneck-shaft angle. The mechanical axis 1910 and anatomic axis 1920 arealso shown. Assessment of these relationships can change the reamingdirection to achieve neutral alignment of the prosthesis with thefemoral canal.

Using anteroposterior and lateral radiographs, measurements are made ofthe proximal and distal geometry to determine the size and optimaldesign of the implant.

Typically, after obtaining surgical access to the hip joint, the femoralneck 1982 is resected, e.g. along the line 1990. Once the neck isresected, the medullary canal is reamed. Reaming can be accomplished,for example, with a conical or straight reamer, or a flexible reamer.The depth of reaming is dictated by the specific design of the implant.Once the canal has been reamed, the proximal reamer is prepared byserial rasping, with the rasp directed down into the canal.

B. Surgical Tools

Further, surgical assistance can be provided by using a device appliedto the outer surface of the articular cartilage or the bone, includingthe subchondral bone, in order to match the alignment of the articularrepair system and the recipient site or the joint. The device can beround, circular, oval, ellipsoid, curved or irregular in shape. Theshape can be selected or adjusted to match or enclose an area ofdiseased cartilage or an area slightly larger than the area of diseasedcartilage or substantially larger than the diseased cartilage. The areacan encompass the entire articular surface or the weight bearingsurface. Such devices are typically preferred when replacement of amajority or an entire articular surface is contemplated.

Mechanical devices can be used for surgical assistance (e.g., surgicaltools), for example using gels, molds, plastics or metal. One or moreelectronic images or intraoperative measurements can be obtainedproviding object coordinates that define the articular and/or bonesurface and shape. These objects' coordinates can be utilized to eithershape the device, e.g. using a CAD/CAM technique, to be adapted to apatient's articular anatomy or, alternatively, to select a typicallypre-made device that has a good fit with a patient's articular anatomy.The device can have a surface and shape that will match all or portionsof the articular cartilage, subchondral bone and/or other bone surfaceand shape, e.g. similar to a “mirror image.” The device can include,without limitation, one or more cut planes, apertures, slots and/orholes to accommodate surgical instruments such as drills, reamers,curettes, k-wires, screws and saws.

The device may have a single component or multiple components. Thecomponents may be attached to the unoperated and operated portions ofthe intra- or extra-articular anatomy. For example, one component may beattached to the femoral neck, while another component may be in contactwith the greater or lesser trochanter. Typically, the differentcomponents can be used to assist with different parts of the surgicalprocedure. When multiple components are used, one or more components mayalso be attached to a different component rather than the articularcartilage, subchondral bone or other areas of osseous or non-osseousanatomy. For example, a tibial mold may be attached to a femoral moldand tibial cuts can be performed in reference to femoral cuts.

Components may also be designed to fit to the joint after an operativestep has been performed. For example, in a knee, one component may bedesigned to fit all or portions of a distal femur before any cuts havebeen made, while another component may be designed to fit on a cut thathas been made with the previously used mold or component. In a hip, onecomponent may be used to perform an initial cut, for example through thefemoral neck, while another subsequently used component may be designedto fit on the femoral neck after the cut, for example covering the areaof the cut with a central opening for insertion of a reamer. Using thisapproach, subsequent surgical steps may also be performed with highaccuracy, e.g. reaming of the marrow cavity.

In another embodiment, a guide may be attached to a mold to control thedirection and orientation of surgical instruments. For example, afterthe femoral neck has been cut, a mold may be attached to the area of thecut, whereby it fits portions or all of the exposed bone surface. Themold may have an opening adapted for a reamer. Before the reamer isintroduced a femoral reamer guide may be inserted into the mold andadvanced into the marrow cavity. The position and orientation of thereamer guide may be determined by the femoral mold. The reamer can thenbe advanced over the reamer guide and the marrow cavity can be reamedwith improved accuracy. Similar approaches are feasible in the knee andother joints.

All mold components may be disposable. Alternatively, some moldscomponents may be re-usable. Typically, mold components applied after asurgical step such as a cut as been performed can be reuseable, since areproducible anatomic interface will have been established.

Interconnecting or bridging components may be used. For example, suchinterconnecting or bridging components may couple the mold attached tothe joint with a standard, preferably unmodified or only minimallymodified cut block used during knee or hip surgery. Interconnecting orbriding components may be made of plastic or metal. When made of metalor other hard material, they can help protect the joint from plasticdebris, for example when a reamer or saw would otherwise get intocontact with the mold.

The accuracy of the attachment between the component or mold and thecartilage or subchondral bone or other osseous structures is typicallybetter than 2 mm, more preferred better than 1 mm, more preferred betterthan 0.7 mm, more preferred better than 0.5 mm, or even more preferredbetter than 0.5 mm. The accuracy of the attachment between differentcomponents or between one or more molds and one or more surgicalinstruments is typically better than 2 mm, more preferred better than 1mm, more preferred better than 0.7 mm, more preferred better than 0.5mm, or even more preferred better than 0.5 mm.

The angular error of any attachments or between any components orbetween components, molds, instruments and/or the anatomic orbiomechanical axes is preferably less than 2 degrees, more preferablyless than 1.5 degrees, more preferably less than 1 degree, and even morepreferably less than 0.5 degrees. The total angular error is preferablyless than 2 degrees, more preferably less than 1.5 degrees, morepreferably less than 1 degree, and even more preferably less than 0.5degrees.

Typically, a position will be chosen that will result in an anatomicallydesirable cut plane, drill hole, or general instrument orientation forsubsequent placement of an articular repair system or for facilitatingplacement of the articular repair system. Moreover, the device can bedesigned so that the depth of the drill, reamer or other surgicalinstrument can be controlled, e.g., the drill cannot go any deeper intothe tissue than defined by the device, and the size of the hole in theblock can be designed to essentially match the size of the implant.Information about other joints or axis and alignment information of ajoint or extremity can be included when selecting the position of theseslots or holes. Alternatively, the openings in the device can be madelarger than needed to accommodate these instruments. The device can alsobe configured to conform to the articular shape. The apertures, oropenings, provided can be wide enough to allow for varying the positionor angle of the surgical instrument, e.g., reamers, saws, drills,curettes and other surgical instruments. An instrument guide, typicallycomprised of a relatively hard material, can then be applied to thedevice. The device helps orient the instrument guide relative to thethree-dimensional anatomy of the joint.

The mold may contact the entire articular surface. In variousembodiments, the mold can be in contact with only a portion of thearticular surface. Thus, the mold can be in contact, without limitation,with: 100% of the articular surface; 80% of the articular surface; 50%of the articular surface; 30% of the articular surface; 30% of thearticular surface; 20% of the articular surface; or 10% or less of thearticular surface. An advantage of a smaller surface contact area is areduction in size of the mold thereby enabling cost efficientmanufacturing and, more important, minimally invasive surgicaltechniques. The size of the mold and its surface contact areas have tobe sufficient, however, to ensure accurate placement so that subsequentdrilling and cutting can be performed with sufficient accuracy.

In various embodiments, the maximum diameter of the mold is less than 10cm. In other embodiments, the maximum diameter of the mold may be lessthan: 8 cm; 5 cm; 4 cm; 3 cm; or even less than 2 cm.

The mold may be in contact with three or more surface points rather thanan entire surface. These surface points may be on the articular surfaceor external to the articular surface. By using contact points ratherthan an entire surface or portions of the surface, the size of the moldmay be reduced.

Reductions in the size of the mold can be used to enable minimallyinvasive surgery (MIS) in the hip, the knee, the shoulder and otherjoints. MIS technique with small molds will help to reduceintraoperative blood loss, preserve tissue including possibly bone,enable muscle sparing techniques and reduce postoperative pain andenable faster recovery. Thus, in one embodiment of the invention themold is used in conjunction with a muscle sparing technique. In anotherembodiment of the invention, the mold may be used with a bone sparingtechnique. In another embodiment of the invention, the mold is shaped toenable MIS technique with an incision size of less than 15 cm, or, morepreferred, less than 13 cm, or, more preferred, less than 10 cm, or,more preferred, less than 8 cm, or, more preferred, less than 6 cm.

The mold may be placed in contact with points or surfaces outside of thearticular surface. For example, the mold can rest on bone in theintercondylar notch or the anterior or other aspects of the tibia or theacetabular rim or the lesser or greater trochanter. Optionally, the moldmay only rest on points or surfaces that are external to the articularsurface. Furthermore, the mold may rest on points or surfaces within theweight-bearing surface, or on points or surfaces external to theweight-bearing surface.

The mold may be designed to rest on bone or cartilage outside the areato be worked on, e.g. cut, drilled etc. In this manner, multiplesurgical steps can be performed using the same mold. For example, in theknee, the mold may be stabilized against portions of the intercondylarnotch, which can be selected external to areas to be removed for totalknee arthroplasty or other procedures. In the hip, the mold may beattached external to the acetabular fossa, providing a reproduciblereference that is maintained during a procedure, for example total hiparthroplasty. The mold may be affixed to the underlying bone, forexample with pins or drills etc.

In additional embodiments, the mold may rest on the articular cartilage.The mold may rest on the subchondral bone or on structures external tothe articular surface that are within the joint space or on structuresexternal to the joint space. If the mold is designed to rest on thecartilage, an imaging test demonstrating the articular cartilage can beused in one embodiment. This can, for example, include ultrasound,spiral CT arthrography, MRI using, for example, cartilage displayingpulse sequences, or MRI arthrography. In another embodiment, an imagingtest demonstrating the subchondral bone, e.g. CT or spiral CT, can beused and a standard cartilage thickness can be added to the scan. Thestandard cartilage thickness can be derived, for example, using ananatomic reference database, age, gender, and race matching, ageadjustments and any method known in the art or developed in the futurefor deriving estimates of cartilage thickness. The standard cartilagethickness may, in some embodiments, be uniform across one or morearticular surfaces or it can change across the articular surface.

The mold may be adapted to rest substantially on subchondral bone. Inthis case, residual cartilage can create some offset and inaccurateresult with resultant inaccuracy in surgical cuts, drilling and thelike. In one embodiment, the residual cartilage is removed in a firststep in areas where the mold is designed to contact the bone and thesubchondral bone is exposed. In a second step, the mold is then placedon the subchondral bone.

With advanced osteoarthritis, significant articular deformity canresult. The articular surface(s) can become flattened. There can be cystformation or osteophyte formation. “Tram track” like structures can formon the articular surface. In one embodiment of the invention,osteophytes or other deformities may be removed by the computer softwareprior to generation of the mold. The software can automatically,semi-automatically or manually with input from the user simulatesurgical removal of the osteophytes or other deformities, and predictthe resulting shape of the joint and the associated surfaces. The moldcan then be designed based on the predicted shape. Intraoperatively,these osteophytes or other deformities can then also optionally beremoved prior to placing the mold and performing the procedure.Alternatively, the mold can be designed to avoid such deformities. Forexample, the mold may only be in contact with points on the articularsurface or external to the articular surface that are not affected orinvolved by osteophytes. The mold can rest on the articular surface orexternal to the articular surface on three or more points or smallsurfaces with the body of the mold elevated or detached from thearticular surface so that the accuracy of its position cannot beaffected by osteophytes or other articular deformities. The mold canrest on one or more tibial spines or portions of the tibial spines.Alternatively, all or portions of the mold may be designed to rest onosteophytes or other excrescences or pathological changes.

The surgeon can, optionally, make fine adjustments between the alignmentdevice and the instrument guide. In this manner, an optimal compromisecan be found, for example, between biomechanical alignment and jointlaxity or biomechanical alignment and joint function, e.g. in a kneejoint flexion gap and extension gap. By oversizing the openings in thealignment guide, the surgeon can utilize the instruments and insert themin the instrument guide without damaging the alignment guide. Thus, inparticular if the alignment guide is made of plastic, debris will not beintroduced into the joint. The position and orientation between thealignment guide and the instrument guide can be also be optimized withthe use of, for example, interposed spacers, wedges, screws and othermechanical or electrical methods known in the art.

A surgeon may desire to influence joint laxity as well as jointalignment. This can be optimized for different flexion and extension,abduction, or adduction, internal and external rotation angles. For thispurpose, for example, spacers can be introduced that are attached orthat are in contact with one or more molds. The surgeon canintraoperatively evaluate the laxity or tightness of a joint usingspacers with different thickness or one or more spacers with the samethickness. For example, spacers can be applied in a knee joint in thepresence of one or more molds and the flexion gap can be evaluated withthe knee joint in flexion. The knee joint can then be extended and theextension gap can be evaluated. Ultimately, the surgeon will select anoptimal combination of spacers for a given joint and mold. A surgicalcut guide can be applied to the mold with the spacers optionallyinterposed between the mold and the cut guide. In this manner, the exactposition of the surgical cuts can be influenced and can be adjusted toachieve an optimal result. Thus, the position of a mold can be optimizedrelative to the joint, bone or cartilage for soft-tissue tension,ligament balancing or for flexion, extension, rotation, abduction,adduction, anteversion, retroversion and other joint or bone positionsand motion. The position of a cut block or other surgical instrument maybe optimized relative to the mold for soft-tissue tension or forligament balancing or for flexion, extension, rotation, abduction,adduction, anteversion, retroversion and other joint or bone positionsand motion. Both the position of the mold and the position of othercomponents including cut blocks and surgical instruments may beoptimized for soft-tissue tension or for ligament balancing or forflexion, extension, rotation, abduction, adduction, anteversion,retroversion and other joint or bone positions and motion.

Someone skilled in the art will recognize other means for optimizing theposition of the surgical cuts or other interventions. As stated above,expandable or ratchet-like devices may be utilized that can be insertedinto the joint or that can be attached or that can touch the mold (seealso FIG. 37D). Such devices can extend from a cutting block or otherdevices attached to the mold, optimizing the position of drill holes orcuts for different joint positions or they can be integrated inside themold. Integration in the cutting block or other devices attached to themold is preferable, since the expandable or ratchet-like mechanisms canbe sterilized and re-used during other surgeries, for example in otherpatients. Optionally, the expandable or ratchet-like devices may bedisposable. The expandable or ratchet like devices may extend to thejoint without engaging or contacting the mold; alternatively, thesedevices may engage or contact the mold. Hinge-like mechanisms areapplicable. Similarly, jack-like mechanisms are useful. In principal,any mechanical or electrical device useful for fine-tuning the positionof the cut guide relative to the molds may be used. These embodimentsare helpful for soft-tissue tension optimization and ligament balancingin different joints for different static positions and during jointmotion.

A surgeon may desire to influence joint laxity as well as jointalignment. This can be optimized for different flexion and extension,abduction, or adduction, internal and external rotation angles. For thispurpose, for example, spacers or expandable or ratchet-like can beutilized that can be attached or that can be in contact with one or moremolds. The surgeon can intraoperatively evaluate the laxity or tightnessof a joint using spacers with different thickness or one or more spacerswith the same thickness or using such expandable or ratchet likedevices. For example, spacers or a ratchet like device can be applied ina knee joint in the presence of one or more molds and the flexion gapcan be evaluated with the knee joint in flexion. The knee joint can thenbe extended and the extension gap can be evaluated. Ultimately, thesurgeon will select an optimal combination of spacers or an optimalposition for an expandable or ratchet-like device for a given joint andmold. A surgical cut guide can be applied to the mold with the spacersor the expandable or ratchet-like device optionally interposed betweenthe mold and the cut guide or, in select embodiments, between the moldand the joint or the mold and an opposite articular surface. In thismanner, the exact position of the surgical cuts can be influenced andcan be adjusted to achieve an optimal result. Someone skilled in the artwill recognize other means for optimizing the position of the surgicalcuts or drill holes. For example, expandable or ratchet-like devices canbe utilized that can be inserted into the joint or that can be attachedor that can touch the mold. Hinge-like mechanisms are applicable.Similarly, jack-like mechanisms are useful. In principal, any mechanicalor electrical device useful for fine-tuning the position of the cutguide relative to the molds can be used.

The template and any related instrumentation such as spacers or ratchetscan be combined with a tensiometer to provide a better intraoperativeassessment of the joint. The tensiometer can be utilized to furtheroptimize the anatomic alignment and tightness of the joint and toimprove post-operative function and outcomes. Optionally, local contactpressures may be evaluated intraoperatively, for example using a sensorlike the ones manufactured by Tekscan, South Boston, Mass. The contactpressures can be measured between the mold and the joint or between themold and any attached devices such as a surgical cut block.

The template may be a mold that can be made of a plastic or polymer. Themold may be produced by rapid prototyping technology, in whichsuccessive layers of plastic are laid down, as know in the art. In otherembodiments, the template or portions of the template can be made ofmetal. The mold can be milled or made using laser based manufacturingtechniques.

The template may be casted using rapid prototyping and, for example,lost wax technique. It may also be milled. For example, a preformed moldwith a generic shape can be used at the outset, which can then be milledto the patient specific dimensions. The milling may only occur on onesurface of the mold, preferably the surface that faces the articularsurface. Milling and rapid prototyping techniques may be combined.

Curable materials may be used which can be poured into forms that are,for example, generated using rapid prototyping. For example, liquidmetal may be used. Cured materials may optionally be milled or thesurface can be further refined using other techniques.

Metal inserts may be applied to plastic components. For example, aplastic mold may have at least one guide aperture to accept a reamingdevice or a saw. A metal insert may be used to provide a hard wall toaccept the reamer or saw. Using this or similar designs can be useful toavoid the accumulation of plastic or other debris in the joint when thesaw or other surgical instruments may get in contact with the mold.Other hard materials can be used to serve as inserts. These can alsoinclude, for example, hard plastics or ceramics.

In another embodiment, the mold does not have metallic inserts to accepta reaming device or saw. The metal inserts or guides may be part of anattached device, that is typically in contact with the mold. A metallicdrill guide or a metallic saw guide may thus, for example, have metallicor hard extenders that reach through the mold thereby, for example, alsostabilizing any devices applied to the mold against the physical body ofthe mold.

The template may not only be used for assisting the surgical techniqueand guiding the placement and direction of surgical instruments. Inaddition, the templates can be utilized for guiding the placement of theimplant or implant components. For example, in the hip joint, tilting ofthe acetabular component is a frequent problem with total hiparthroplasty. A template can be applied to the acetabular wall with anopening in the center large enough to accommodate the acetabularcomponent that the surgeon intends to place. The template can havereceptacles or notches that match the shape of small extensions that canbe part of the implant or that can be applied to the implant. Forexample, the implant can have small members or extensions applied to thetwelve o'clock and six o'clock positions. See, for example, FIG. 9A-D,discussed below. By aligning these members with notches or receptaclesin the mold, the surgeon can ensure that the implant is inserted withouttilting or rotation. These notches or receptacles can also be helpful tohold the implant in place while bone cement is hardening in cementeddesigns.

One or more templates can be used during the surgery. For example, inthe hip, a template can be initially applied to the proximal femur thatclosely approximates the 3D anatomy prior to the resection of thefemoral head. The template can include an opening to accommodate a saw(see FIGS. 8-9). The opening is positioned to achieve an optimallyplaced surgical cut for subsequent reaming and placement of theprosthesis. A second template can then be applied to the proximal femurafter the surgical cut has been made. The second template can be usefulfor guiding the direction of a reamer prior to placement of theprosthesis. As can be seen in this, as well as in other examples,templates can be made for joints prior to any surgical intervention.However, it is also possible to make templates that are designed to fitto a bone or portions of a joint after the surgeon has already performedselected surgical procedures, such as cutting, reaming, drilling, etc.The template can account for the shape of the bone or the jointresulting from these procedures.

In certain embodiments, the surgical assistance device comprises anarray of adjustable, closely spaced pins (e.g., plurality ofindividually moveable mechanical elements). One or more electronicimages or intraoperative measurements can be obtained providing objectcoordinates that define the articular and/or bone surface and shape.These objects' coordinates can be entered or transferred into thedevice, for example manually or electronically, and the information canbe used to create a surface and shape that will match all or portions ofthe articular and/or bone surface and shape by moving one or more of theelements, e.g. similar to an “image.” The device can include slots andholes to accommodate surgical instruments such as drills, curettes,k-wires, screws and saws. The position of these slots and holes may beadjusted by moving one or more of the mechanical elements. Typically, aposition will be chosen that will result in an anatomically desirablecut plane, reaming direction, or drill hole or instrument orientationfor subsequent placement of an articular repair system or forfacilitating the placement of an articular repair system.

Information about other joints or axis and alignment information of ajoint or extremity can be included when selecting the position of the,without limitation, cut planes, apertures, slots or holes on thetemplate, in accordance with an embodiment of the invention. Thebiomechanical and/or anatomic axes may be derived using above-describedimaging techniques including, without limitation, a standard radiograph,including a load bearing radiograph, for example an upright knee x-rayor a whole leg length film (e.g., hip to foot) These radiographs may beacquired in different projections, for example anteroposterior,posteroanterior, lateral, oblique etc. The biomechanical and anatomicaxes may also be derived using other imaging modalities such as CT scanor MRI scan, a CT scout scan or MRI localized scans through portions orall of the extremity, either alone or in combination, as described inabove embodiments. For example, when total or partial knee arthroplastyis contemplated, a spiral CT scan may be obtained through the kneejoint. The spiral CT scan through the knee joint serves as the basis forgenerating the negative contour template(s)/mold(s) that will be affixedto portions or all of the knee joint. Additional CT or MRI scans may beobtained through the hip and ankle joint. These may be used to definethe centroids or centerpoints in each joint or other anatomic landmarks,for example, and then to derive the biomechanical and other axes.

In another embodiment, the biomechanical axis may be established usingnon-image based approaches including traditional surgical instrumentsand measurement tools such as intramedullary rods, alignment guides andalso surgical navigation. For example, in a knee joint, optical orradiofrequency markers can be attached to the extremity. The lower limbmay then be rotated around the hip joint and the position of the markerscan be recorded for different limb positions. The center of the rotationwill determine the center of the femoral head. Similar reference pointsmay be determined in the ankle joint etc. The position of the templatesor, more typically, the position of surgical instruments relative to thetemplates may then be optimized for a given biomechanical load pattern,for example in varus or valgus alignment. Thus, by performing thesemeasurements pre- or intraoperatively, the position of the surgicalinstruments may be optimized relative to the molds and the cuts can beplaced to correct underlying axis errors such as varus or valgusmalalignment or ante- or retroversion.

Upon imaging, a physical template of a joint, such as a knee joint, orhip joint, or ankle joint or shoulder joint is generated, in accordancewith an embodiment of the invention. The template can be used to performimage guided surgical procedures such as partial or complete jointreplacement, articular resurfacing, or ligament repair. The template mayinclude reference points or opening or apertures for surgicalinstruments such as drills, saws, burrs and the like.

In order to derive the preferred orientation of drill holes, cut planes,saw planes and the like, openings or receptacles in said template orattachments will be adjusted to account for at least one axis. The axiscan be anatomic or biomechanical, for example, for a knee joint, a hipjoint, an ankle joint, a shoulder joint or an elbow joint.

In one embodiment, only a single axis is used for placing and optimizingsuch drill holes, saw planes, cut planes, and or other surgicalinterventions. This axis may be, for example, an anatomical orbiomechanical axis. In a preferred embodiment, a combination of axisand/or planes can be used for optimizing the placement of the drillholes, saw planes, cut planes or other surgical interventions. Forexample, two axes (e.g., one anatomical and one biomechanical) can befactored into the position, shape or orientation of the 3D guidedtemplate and related attachments or linkages. For example, two axes,(e.g., one anatomical and biomechanical) and one plane (e.g., the topplane defined by the tibial plateau), can be used. Alternatively, two ormore planes can be used (e.g., a coronal and a sagittal plane), asdefined by the image or by the patients anatomy.

Angle and distance measurements and surface topography measurements maybe performed in these one or more, preferably two or more, preferablythree or more multiple planes, as necessary. These angle measurementscan, for example, yield information on varus or valgus deformity,flexion or extension deficit, hyper or hypo-flexion or hyper- orhypo-extension, abduction, adduction, internal or external rotationdeficit, or hyper- or hypo-abduction, hyper- or hypo-adduction, hyper-or hypo-internal or external rotation.

Single or multi-axis line or plane measurements can then be utilized todetermine preferred angles of correction, e.g., by adjusting surgicalcut or saw planes or other surgical interventions. Typically, two axiscorrections will be preferred over a single axis correction, a two planecorrection will be preferred over a single plane correction and soforth.

In accordance with another embodiment of the invention, more than onedrilling, cut, boring and/or reaming or other surgical intervention isperformed for a particular treatment such as the placement of a jointresurfacing or replacing implant, or components thereof. These two ormore surgical interventions (e.g., drilling, cutting, reaming, sawing)are made in relationship to a biomechanical axis, and/or an anatomicalaxis and/or an implant axis. The 3D guidance template or attachments orlinkages thereto include two or more openings, guides, apertures orreference planes to make at least two or more drillings, reamings,borings, sawings or cuts in relationship to a biomechanical axis, ananatomical axis, an implant axis or other axis derived therefrom orrelated thereto.

While in simple embodiments it is possible that only a single cut ordrilling will be made in relationship to a biomechanical axis, ananatomical axis, an implant axis and/or an axis related thereto, in mostmeaningful implementations, two or more drillings, borings, reamings,cutting and/or sawings will be performed or combinations thereof inrelationship to a biomechanical, anatomical and/or implant axis.

For example, an initial cut may be placed in relationship to abiomechanical axis of particular joint. A subsequent drilling, cut orother intervention can be performed in relation to an anatomical axis.Both can be designed to achieve a correction in a biomechanical axisand/or anatomical axis. In another example, an initial cut can beperformed in relationship to a biomechanical axis, while a subsequentcut is performed in relationship to an implant axis or an implant plane.Any combination in surgical interventions and in relating them to anycombination of biomechanical, anatomical, implant axis or planes relatedthereto is possible. In many embodiments of the invention, it isdesirable that a single cut or drilling be made in relationship to abiomechanical or anatomical axis. Subsequent cuts or drillings or othersurgical interventions can then be made in reference to said firstintervention. These subsequent interventions can be performed directlyoff the same 3D guidance template or they can be performed by attachingsurgical instruments or linkages or reference frames or secondary orother templates to the first template or the cut plane or hole and thelike created with the first template.

FIG. 22 shows an example of a surgical tool 410 having one surface 400matching the geometry of an articular surface of the joint. Also shownis an aperture 415 in the tool 410 capable of controlling drill depthand width of the hole and allowing implantation or insertion of implant420 having a press-fit design.

In another embodiment, a frame can be applied to the bone or thecartilage in areas other than the diseased bone or cartilage. The framecan include holders and guides for surgical instruments. The frame canbe attached to one or preferably more previously defined anatomicreference points. Alternatively, the position of the frame can becross-registered relative to one, or more, anatomic landmarks, using animaging test or intraoperative measurement, for example one or morefluoroscopic images acquired intraoperatively. One or more electronicimages or intraoperative measurements including using mechanical devicescan be obtained providing object coordinates that define the articularand/or bone surface and shape. These objects' coordinates can be enteredor transferred into the device, for example manually or electronically,and the information can be used to move one or more of the holders orguides for surgical instruments. Typically, a position will be chosenthat will result in a surgically or anatomically desirable cut plane ordrill hole orientation for subsequent placement of an articular repairsystem. Information about other joints or axis and alignment informationof a joint or extremity can be included when selecting the position ofthese slots or holes.

Furthermore, re-useable tools (e.g., molds) can be also be created andemployed. Non-limiting examples of re-useable materials include puttiesand other deformable materials (e.g., an array of adjustable closelyspaced pins that can be configured to match the topography of a jointsurface). In other embodiments, the molds may be made using balloons.The balloons can optionally be filled with a hardening material. Asurface can be created or can be incorporated in the balloon that allowsfor placement of a surgical cut guide, reaming guide, drill guide orplacement of other surgical tools. The balloon or other deformablematerial can be shaped intraoperatively to conform to at least onearticular surface. Other surfaces can be shaped in order to be parallelor perpendicular to anatomic or biomechanical axes. The anatomic orbiomechanical axes can be found using an intraoperative imaging test orsurgical tools commonly used for this purpose in hip, knee or otherarthroplasties.

In various embodiments, the template may include a reference element,such as a pin, that upon positioning of the template on the articularsurface, establishes a reference plane relative to a biomechanical axisor an anatomical axis or plane of a limb. For example, in a knee surgerythe reference element may establish a reference plane from the center ofthe hip to the center of the ankle. In other embodiments, the referenceelement may establish an axis that subsequently be used a surgical toolto correct an axis deformity.

In these embodiments, the template can be created directly from thejoint during surgery or, alternatively, created from an image of thejoint, for example, using one or more computer programs to determineobject coordinates defining the surface contour of the joint andtransferring (e.g., dialing-in) these co-ordinates to the tool.Subsequently, the tool can be aligned accurately over the joint and,accordingly, the surgical instrument guide or the implant will be moreaccurately placed in or over the articular surface.

In both single-use and re-useable embodiments, the tool can be designedso that the instrument controls the depth and/or direction of the drill,i.e., the drill cannot go any deeper into the tissue than the instrumentallows, and the size of the hole or aperture in the instrument can bedesigned to essentially match the size of the implant. The tool can beused for general prosthesis implantation, including, but not limited to,the articular repair implants described herein and for reaming themarrow in the case of a total arthroplasty.

These surgical tools (devices) can also be used to remove an area ofdiseased cartilage and underlying bone or an area slightly larger thanthe diseased cartilage and underlying bone. In addition, the device canbe used on a “donor,” e.g., a cadaveric specimen, to obtain implantablerepair material. The device is typically positioned in the same generalanatomic area in which the tissue was removed in the recipient. Theshape of the device is then used to identify a donor site providing aseamless or near seamless match between the donor tissue sample and therecipient site. This can be achieved by identifying the position of thedevice in which the articular surface in the donor, e.g. a cadavericspecimen, has a seamless or near seamless contact with the inner surfacewhen applied to the cartilage.

The device can be molded, rapid prototyped, machine and/or formed basedon the size of the area of diseased cartilage and based on the curvatureof the cartilage or the underlying subchondral bone or a combination ofboth or using adjacent structures inside or external to the joint space.The device can take into consideration surgical removal of, for example,the meniscus, in arriving at a joint surface configuration.

In one embodiment, the device can then be applied to the donor, (e.g., acadaveric specimen) and the donor tissue can be obtained with use of ablade or saw or other tissue removing device. The device can then beapplied to the recipient in the area of the joint and the diseasedcartilage, where applicable, and underlying bone can be removed with useof a blade or saw or other tissue cutting device whereby the size andshape of the removed tissue containing the diseased cartilage willclosely resemble the size and shape of the donor tissue. The donortissue can then be attached to the recipient site. For example, saidattachment can be achieved with use of screws or pins (e.g., metallic,non-metallic or bioresorable) or other fixation means including but notlimited to a tissue adhesive. Attachment can be through the cartilagesurface or alternatively, through the marrow space.

The implant site can be prepared with use of a robotic device. Therobotic device can use information from an electronic image forpreparing the recipient site.

Identification and preparation of the implant site and insertion of theimplant can be supported by a surgical navigation system. In such asystem, the position or orientation of a surgical instrument withrespect to the patient's anatomy can be tracked in real-time in one ormore 2D or 3D images. These 2D or 3D images can be calculated fromimages that were acquired preoperatively, such as MR or CT images.Non-image based surgical navigation systems that find axes or anatomicalstructures, for example with use of joint motion, can also be used. Theposition and orientation of the surgical instrument as well as the moldincluding alignment guides, surgical instrument guides, reaming guides,drill guides, saw guides, etc. can be determined from markers attachedto these devices. These markers can be located by a detector using, forexample, optical, acoustical or electromagnetic signals.

Identification and preparation of the implant site and insertion of theimplant can also be supported with use of a C-arm system. The C-armsystem can afford imaging of the joint in one or, preferably, multipleplanes. The multiplanar imaging capability can aid in defining the shapeof an articular surface. This information can be used to selected animplant with a good fit to the articular surface. Currently availableC-arm systems also afford cross-sectional imaging capability, forexample for identification and preparation of the implant site andinsertion of the implant. C-arm imaging can be combined withadministration of radiographic contrast.

In various embodiments, the surgical devices described herein caninclude one or more materials that harden to form a mold of thearticular surface. In preferred embodiments, the materials used arebiocompatible, such as, without limitation, acylonitrile butadienestyrene, polyphenylsulfone and polycarbonate. As used herein“biocompatible” shall mean any material that is not toxic to the body(e.g., produces a negative reaction undert ISO 10993 standards,incorporated herein by reference). In various embodiments, thesebiocompatible materials may be compatible with rapid prototypingtechniques.

In further embodiments, the mold material is capable of heatsterilization without deformation. An exemplary mold material ispolyphenylsulfone, which does not deform up to a temperature of 207°celcius. Alternatively, the mold may be capable of sterilization usinggases, e.g. ethyleneoxide. The mold may be capable of sterilizationusing radiation, e.g. γ-radiation. The mold may be capable ofsterilization using hydrogen peroxide or other chemical means. The moldmay be capable of sterilization using any one or more methods ofsterilization known in the art or developed in the future.

A wide-variety of materials capable of hardening in situ includepolymers that can be triggered to undergo a phase change, for examplepolymers that are liquid or semi-liquid and harden to solids or gelsupon exposure to air, application of ultraviolet light, visible light,exposure to blood, water or other ionic changes. (See, also, U.S. Pat.No. 6,443,988 to Felt et al. issued Sep. 3, 2002 and documents citedtherein). Non-limiting examples of suitable curable and hardeningmaterials include polyurethane materials (e.g., U.S. Pat. No. 6,443,988to Felt et al., U.S. Pat. No. 5,288,797 to Khalil issued Feb. 22, 1994,U.S. Pat. No. 4,098,626 to Graham et al. issued Jul. 4, 1978 and U.S.Pat. No. 4,594,380 to Chapin et al. issued Jun. 10, 1986; and Lu et al.(2000) BioMaterials 21(15):1595-1605 describing porous poly(L-lactideacid foams); hydrophilic polymers as disclosed, for example, in U.S.Pat. No. 5,162,430; hydrogel materials such as those described in Wakeet al. (1995) Cell Transplantation 4(3):275-279, Wiese et al. (2001) J.Biomedical Materials Research 54(2):179-188 and Marler et al. (2000)Plastic Reconstruct. Surgery 105(6):2049-2058; hyaluronic acid materials(e.g., Duranti et al. (1998) Dermatologic Surgery 24(12):1317-1325);expanding beads such as chitin beads (e.g., Yusof et al. (2001) J.Biomedical Materials Research 54(1):59-68); crystal free metals such asLiquidmetals®, and/or materials used in dental applications (See, e.g.,Brauer and Antonucci, “Dental Applications” pp. 257-258 in “ConciseEncyclopedia of Polymer Science and Engineering” and U.S. Pat. No.4,368,040 to Weissman issued Jan. 11, 1983). Any biocompatible materialthat is sufficiently flowable to permit it to be delivered to the jointand there undergo complete cure in situ under physiologically acceptableconditions can be used. The material can also be biodegradable.

The curable materials can be used in conjunction with a surgical tool asdescribed herein. For example, the surgical tool can be a template thatincludes one or more apertures therein adapted to receive injections andthe curable materials can be injected through the apertures. Prior tosolidifying in situ the materials will conform to the articular surface(subchondral bone and/or articular cartilage) facing the surgical tooland, accordingly, will form a mirror image impression of the surfaceupon hardening, thereby recreating a normal or near normal articularsurface.

In addition, curable materials or surgical tools can also be used inconjunction with any of the imaging tests and analysis described herein,for example by molding these materials or surgical tools based on animage of a joint. For example, rapid prototyping may be used to performautomated construction of the template. The rapid prototyping mayinclude the use of, without limitation, 3D printers, stereolithographymachines or selective laser sintering systems. Rapid prototyping is atypically based on computer-aided manufacturing (CAM). Although rapidprototyping traditionally has been used to produce prototypes, they arenow increasingly being employed to produce tools or even to manufactureproduction quality parts. In an exemplary rapid prototyping method, amachine reads in data from a CAD drawing, and lays down successivemillimeter-thick layers of plastic or other engineering material, and inthis way the template can be built from a long series of cross sections.These layers are glued together or fused (often using a laser) to createthe cross section described in the CAD drawing.

FIG. 23 is a flow chart illustrating the steps involved in designing amold for use in preparing a joint surface. Optionally, the first stepcan be to measure the size of the area of the diseased cartilage orcartilage loss 2100, Once the size of the cartilage loss has beenmeasured, the user can measure the thickness of the adjacent cartilage2120, prior to measuring the curvature of the articular surface and/orthe subchondral bone 2130. Alternatively, the user can skip the step ofmeasuring the thickness of the adjacent cartilage 2102. Once anunderstanding and determination of the shape of the subchondral bone isdetermined, either a mold can be selected from a library of molds 3132or a patient specific mold can be generated 2134. In either event, theimplantation site is then prepared 2140 and implantation is performed2142. Any of these steps can be repeated by the optional repeat steps2101, 2121, 2131, 2133, 2135, 2141.

A variety of techniques can be used to derive the shape of the template,as described above. For example, a few selected CT slices through thehip joint, along with a full spiral CT through the knee joint and a fewselected slices through the ankle joint can be used to help define theaxes if surgery is contemplated of the knee joint. Once the axes aredefined, the shape of the subchondral bone can be derived, followed byapplying standardized cartilage loss.

Methodologies for stabilizing the 3D guidance templates will now bedescribed. The 3D guide template may be stabilized using multiplesurgical tools such as, without limitation: K-wires, a drill bitanchored into the bone and left within the template to stabilize itagainst the bone; one or more convexities or cavities on the surfacefacing the cartilage; bone stabilization against intra/extra articularsurfaces, optionally with extenders, for example, from an articularsurface onto an extra-articular surface; and/or stabilization againstnewly placed cuts or other surgical interventions.

Specific anatomic landmarks may be selected in the design and make ofthe 3D guide template in order to further optimize the anatomicstabilization. For example, a 3D guidance template may be designed tocover portions or all off an osteophyte or bone spur in order to enhanceanchoring of the 3D guide template against the underlying articularanatomy. The 3D guidance template may be designed to the shape of atrochlear or intercondylar notch and can encompass multiple anatomicareas such as a trochlea, a medial and a lateral femoral condyle at thesame time. In the tibia, a 3D guide template may be designed toencompass a medial and lateral tibial plateau at the same time and itcan optionally include the tibial spine for optimized stabilization andcross-referencing. In a hip, the fovea capitis may be utilized in orderto stabilize a 3D guide template. Optionally, the surgeon may elect toresect the ligamentum capitis femoris in order to improve thestabilization. Also in the hip, an acetabular mold can be designed toextend into the region of the tri-radiate cartilage, the medial,lateral, superior, inferior, anterior and posterior acetabular wall orring. By having these extensions and additional features forstabilization, a more reproducible position of the 3D template can beachieved with resulted improvement in accuracy of the surgicalprocedure. Typically, a template with more than one convexity orconcavity or multiple convexities or concavities will provide bettercross-referencing in the anatomic surface and higher accuracy and higherstabilization than compared to a mold that has only few surface featuressuch as a singular convexity. Thus, in order to improve theimplementation and intraoperative accuracy, careful surgical planningand preoperative planning is desired, that encompasses preferably morethan one convexity, more preferred more than two convexities and evenmore preferred more than three convexities, or that encompasses morethan one concavity, more preferred more than two concavities or evenmore preferred more than three concavities on an articular surface oradjoined surface, including bone and cartilage outside theweight-bearing surface.

In an even more preferred embodiment, more than one convexity andconcavity, more preferred more than two convexities and concavities andeven more preferred more then three convexities and concavities areincluded in the surface of the mold in order to optimize theinteroperative cross-referencing and in order to stabilize the moldprior to any surgical intervention.

Turning now to particular 3D surgical template configurations and totemplates for specific joint applications which are intended to teachthe concept of the design as it would then apply to other joints in thebody:

i. 3D Guidance Template Configurations/Positioning

The 3D guidance template may include a surface that duplicates the innersurface of an implant or an implant component, and/or that conforms toan articular surface, at least partially, in accordance with anembodiment of the invention. More than one of the surfaces of thetemplate may match or conform to one or more of the surfaces or portionsof one or more of these surfaces of an implant, implant component,and/or articular surface.

FIG. 30 shows an example of a 3D guidance template 3000 in a hip joint,in accordance with one embodiment of the invention, wherein the templatehas extenders 3010 extending beyond the margin of the joint to providefor additional stability and to fix the template in place. The surfaceof the template facing the joint 3020 is a mirror image of a portion ofthe joint that is not affected by the arthritic process 3030. Bydesigning the template to be a mirror image of at least a portion of thejoint that is not affected by the arthritic process, greaterreproducibility in placing the template can be achieved. In this design,the template spares the arthritic portions 3040 of the joint and doesnot include them in its joint facing surface. The template canoptionally have metal sleeves 3050 to accommodate a reamer or othersurgical instruments, to protect a plastic. The metal sleeves or,optionally, the template can also include stops 3060 to limit theadvancement of a surgical instrument once a predefined depth has beenreached.

FIG. 31 shows another embodiment of a 3D guidance template 3100 for anacetabulum, in accordance with an embodiment of the invention. Thearticular surface is roughened 3110 in some sections by the arthriticprocess. At least a portion of the template 3120 is made to be a mirrorimage of the articular surface altered by the arthritic process 3110. Bymatching the template to the joint in areas where it is altered by thearthritic process improved intraoperative localization and improvedfixation can be achieved. In other section, the template can be matchedto portions of the joint that are not altered by the arthritic process3130.

FIG. 32 shows another embodiment of a 3D guidance template 3200 designedto guide a posterior cut 3210 using a posterior reference plane 3220.The joint facing surface of the template 3230 is, at least in part, amirror image of portions of the joint that are not altered by thearthritic process. The arthritic process includes an osteophyte 3240.The template includes a recess 3250 that helps avoid the osteophyte3240. The template is at least in part substantially matched to portionsof the joint that are not involved by the arthritic process.

FIG. 33 shows another embodiment of a 3D guidance template 3300 designedto guide an anterior cut 3310 using an anterior reference plane 3320.The joint facing surface of the template 3230 is, at least in part, amirror image of portions of the joint that are altered by the arthriticprocess. The arthritic process includes an osteophyte 3240. The jointfacing surface of the template 3230 is a mirror image of the arthriticprocess, at least in part, including the osteophyte 3240. The templateis at least in part substantially matched to portions of the joint thatare involved by the arthritic process.

FIG. 34 shows another embodiment of a 3D guidance template 3400 forguiding a tibial cut (not shown), wherein the tibia 3410 includes anarthritic portion 3420, in this example a subchondral cyst 3430. Thetemplate is designed to avoid the arthritic process by spanning across3440 the defect or cyst.

FIG. 35 shows another embodiment of a 3D guidance template 3500 forguiding a tibial cut (not shown), wherein the tibia 3510 includes anarthritic portion 3520, in this example a subchondral cyst 3530. Thetemplate is designed to include the arthritic process 3520 by extendinginto 3540 the defect or cyst 3530. The surface of the template facingthe joint 3550 is a mirror image of portions of normal joint 3560 andportions of the joint that are altered by the arthritic process 3530.The interface between normal and arthritic tissue is included in theshape of the template 3520.

FIGS. 36A-D show a knee joint with a femoral condyle 3600 including anormal 3610 and arthritic 3620 region, in accordance with variousembodiments of the invention. The interface 3630 between normal 3610 andarthritic 3620 tissue is shown. The template is designed to guide aposterior cut 3640 using a guide plane 3650 or guide aperture 3660.

In one embodiment shown in FIG. 36A the surface of the template facingthe joint 3670 is a mirror image of at least portions of the surface ofthe joint that is healthy or substantially unaffected by the arthriticprocess. A recessed area 3670 can be present to avoid contact with thediseased joint region. This design can be favorable when an imaging testis used that does not provide sufficient detail about the diseasedregion of the joint to accurately generate a template.

In a similar embodiment shown in FIG. 36B the surface of the templatefacing the joint 3670 is a mirror image of at least portions of thesurface of the joint that is healthy or substantially unaffected by thearthritic process. The diseased area 3620 is covered by the template,but the template is not substantially in contact with it.

In another embodiment shown in FIG. 36C the surface of the templatefacing the joint 3670 is a mirror image of at least portions of thesurface of the joint that are arthritic. The diseased area 3620 iscovered by the template, and the template is in close contact with it.This design can be advantageous to obtain greater accuracy inpositioning the template if the arthritic area is well defined on theimaging test, e.g. with high resolution spiral CT or near isotropic MRIacquisitions or MRI with image fusion. This design can also provideenhanced stability during surgical interventions by more firmly fixingthe template against the irregular underlying surface.

In another embodiment shown in FIG. 36D the surface of the templatefacing the joint 3670 is a mirror image of at least portions of thesurface of the joint that are arthritic. The diseased area 3620 iscovered by the template, and the template is in close contact with it.Moreover, healthy or substantially normal regions 3610 are covered bythe template and the template is in close contact with them. Thetemplate is also closely mirroring the shape of the interface betweensubstantially normal or near normal and diseased joint tissue 3630. Thisdesign can be advantageous to obtain even greater accuracy inpositioning the template due to the change in surface profile or contourat the interface and resultant improved placement of the template on thejoint surface. This design can also provide enhanced stability duringsurgical interventions by more firmly fixing and anchoring the templateagainst the underlying surface and the interface 3630.

The template may include guide apertures or reference points for two ormore planes, or at least one of a cut plane and one of a drill hole orreaming opening for a peg or implant stem, in accordance with anembodiment of the invention.

The distance between two opposing, articulating implant components maybe optimized intraoperatively for different pose angles of the joint orjoint positions, such as different degrees of section, extension,abduction, adduction, internal and external rotation. For example,spacers, typically at least partially conforming to the template, may beplaced between the template of the opposite surface, where the oppositesurface can be the native, uncut joint, the cut joint, the surgicallyprepared joint, the trial implant, or the definitive implant componentfor that articular surface. Alternatively, spacers may be placed betweenthe template and the articular surface for which it will enablesubsequent surgical interventions. For example, by placing spacersbetween a tibial template and the tibia, the tibial cut height can beoptimized. The thicker the spacer, or the more spacers interposedbetween the tibial template and the tibial plateau the less deep the cutwill be, i.e. the less bone will be removed from the top of the tibia.

The spacers may be non-conforming to the template, e.g. they may be of aflat nature. The spacers may be convex or concave or include multipleconvexities or concavities. The spacers may be partially conforming tothe template. For example, in one embodiment, the surface of the spaceroptionally facing the articular surface can be molded and individualizedto the articular surface, thereby forming a template/mold, while theopposite surface of the spacer can be flat or curved or have any othernon-patient specific design. The opposite surface may allow forplacement of blocks or other surgical instruments or for linkages toother surgical instruments and measurement devices.

In another embodiment, the template may include multiple slots spaced atequal distance or at variable distances wherein these slots allow toperform cuts at multiple cut heights or cut depths that can be decidedon intraoperatively. In another embodiment, the template may include aratchet-like mechanism wherein the ratchet can be placed between thearticular surface and the template or between the template and theopposite surface wherein the opposite surface may include the native,uncut opposite surface, the cut opposite surface, an opposite surfacetemplate, a trial implant or the implant component designed for theopposite surface. By using a ratchet-like device, soft tissue tensioncan be optimized, for example, for different pose angles of the joint orjoint positions such as flexion, extension, abduction, adduction,internal rotation and external rotation at one or more degrees for eachdirection.

Optimizing soft tissue tension will improve joint function thatadvantageously enhances postoperative performance. Soft tissue tensionmay, for example, be optimized with regard to ligament tension or muscletension but also capsular tension. In the knee joint, soft tissuetension optimization includes typically ligament balancing, e.g. thecruciate ligaments and/or the collateral ligaments, for differentdegrees of knee flexion and knee extension.

In a preferred embodiment, a 3D guidance template may attach to two ormore points on the joint. In an even more preferred embodiment, atemplate may attach to three or more points on the joint, even morepreferred four or more points on the joint, even more preferred five ormore points on the joint, even more preferred six or more points on thejoint, even more preferred seven or more points on the joint, even morepreferred ten or more points on the joint, even more preferred portionsfor the entire surface to be replaced.

In another embodiment, the template may include one or more linkages forsurgical instruments. The linkages may also be utilized for attachingother measurement devices such as alignment guides, intramedullaryguides, laser pointing devices, laser measurement devices, opticalmeasurement devices, radio frequency measurement devices, surgicalnavigation and the like. Someone skilled in the art will recognize manysurgical instruments and measurement in alignment devices may beattached to the template. Alternatively, these surgical instruments oralignment devices may be included within the template.

In another embodiment, a link or a linkage may be attached or may beincorporated or may be part of a template that rests on a firstarticular surface. Said link or linkage may further extend to a secondarticular surface which is typically an opposing articular surface. Saidlink or linkage can thus help cross-reference the first articularsurface with the second articular surface, ultimately assisting theperformance of surgical interventions on the second articular surfaceusing the cross reference to the first articular surface. The secondarticular surface may optionally be cut with a second template.Alternatively, the second articular surface may be cut using a standardsurgical instrument, non-individualized, that is cross referenced viathe link to the surgical mold placed on the first articular surface. Thelink or linkage may include adjustment means, such as ratchets,telescoping devices and the like to optimize the spatial relationshipbetween the first articular surface and the second, opposing articularsurface. This optimization may be performed for different degrees ofjoint flexion, extension, abduction, adduction and rotation.

In another embodiment, the linkage may be made to the cut articularsurface or, more general, an articular surface that has been alteredusing a template and related surgical intervention. Thus, crossreference can be made from the first articular surface from a moldattached to said first articular surface, the mold attached to asurgically altered, for example, cut articular surface, the surgicalinstrument attached to said articular surface altered using the mold,e.g. cut or drilled, and the like. Someone skilled in the art willeasily recognize multiple different variations of this approach.Irrespective of the various variations, in a first step the articularsurface is surgically altered, for example, via cutting, drilling orreaming using a mold while in the second step cross reference isestablished with a second articular surface.

By establishing cross reference between said first and said secondarticular surface either via the template and/or prior to or after asurgical intervention, the surgical intervention performed on the secondarticular surface can be performed using greater accuracy and improvedusability in relation to said articulating, opposing first articularsurface.

FIGS. 37A-D show multiple templates with linkages on the same articularsurface (A-C) and to an opposing articular surface (D), in accordancewith various embodiments of the invention. The biomechanical axis isdenoted as 3700. A horizontal femoral cut 3701, an anterior femoral cut3702, a posterior femoral cut 3703, an anterior chamfer cut 3704 and aposterior chamfer cut 3705 are planned in this example. A first template3705 is applied in order to determine the horizontal cut plane and toperform the cut. The cut is perpendicular to the biomechanical axis3700. The first template 3705 has linkages or extenders 3710 forconnecting a second template 3715 for the anterior cut 3702 and forconnecting a third template 3720 for the posterior cut 3703. Thelinkages 3710 connecting the first template 3705 with the second 3715and third template 3720 help in achieving a reproducible position of thetemplates relative to each other. At least one of the templates,preferably the first template 3705, will have a surface 3706 that is amirror image of the articular surface 3708. In this example, all threetemplates have surface facing the joint that is a mirror image of thejoint, although one template having a surface conforming to the jointsuffices in many applications of the invention.

A fourth template 3725 may optionally be used in order to perform ananterior chamfer cut 3704. The fourth template may have a guide apertureor reference plane 3730 that can determine the anterior chamfer cut3704. The fourth template can, but must not have at least one surface3735 matching one or more cut articular surfaces 3740. The fourthtemplate may have one or more outriggers or extenders 3745 stabilizingthe template against the cut or uncut articular surface.

A fifth template 3750 may optionally be used to perform a anteriorchamfer cut 3705. The fifth template may have a guide aperture orreference plane 3755 that can determine the posterior chamfer cut 3705.The fifth template may have at least one surface 3735 matching one ormore cut articular surfaces 3740. Oblique planes 3760 may help tofurther stabilize the template during the procedure. The fifth templatemay have one or more outriggers or extenders 3745 stabilizing thetemplate against the cut or uncut articular surface.

In another embodiment, an opposite articular side 3765 may be cut inreference to a first articular side 3766. Any order or sequence ofcutting is possible: femur first then tibia, tibia first then femur,patella first, and so forth. A template 3770 may be shaped to the uncutor, in this example, cut first articular side. The template may havestabilizers against the first articular surface, for example withextenders 3772 into a previously created peg hole 3773 for an implant.The template may have a linkage or an extender 3775 to a secondarticular surface 3765. Surgical instruments may be attached to thelinkage or extender 3775. In this example, a tibial cut guide 3778 withmultiple apertures or reference planes 3779 for a horizontal tibial cutis attached. The tibial cut guide may but may not have a surfacematching the tibial surface.

By referencing a first, e.g. femoral, to a second, e.g. tibial cutgreater accuracy can be achieved in the alignment of these cuts, whichwill result in improved implant component alignment and less wear.Ratchet like devices 3785 or hinge like devices or spacers may beinserted into the space between the first and the second articularsurface and soft-tissue tension and ligament balancing can be evaluatedfor different distances achieved between the first 3766 and second 3765articular surface, with one or more of them being cut or uncut. In thismanner, soft-tissue tension and ligament balancing can be tested duringdifferent pose angles, e.g. degrees of flexion or extension. Optionally,tensiometers can be used. Once an ideal soft-tissue tension and/orligament balancing has been achieved, the tibial cut may be performedthrough one of the guide apertures 3779 in reference to the femoral cut.

FIG. 38 is an example demonstrating a deviation in the AP plane of thefemoral 3801 and tibial 3803 axes in a patient. Axis deviations can bedetermined in any desired plane including the AP plane, not only the MLplane. The axis deviation can be measured. The desired correction can bedetermined and the position, orientation and shape of a 3D guidancetemplate can be adjusted in order to achieve the necessary correction.The correction may, for example, be designed to achieve a result whereinthe femoral 3801 and tibial 3803 axes will coincide with thebiomechanical axis 3805.

The invention optionally provides for trial implants and trial devicesthat help test intraoperatively the result of the surgical interventionachieved using the 3D guidance mold. Trial implants or devices can beparticularly useful for subsequent adjustments and fine-tuning of thesurgical intervention, for example, optimizing soft tissue tension indifferent articular pose angles.

In another embodiment, the templates may also allow for intraoperativeadjustments. For example, the template may include an opening for a pin.The pin can be placed in the bone and the template can be rotated aroundthe pin thereby optimizing, for example, medial and lateral ligamenttension in a knee joint or thereby optimizing the cut orientation andresultant rotation and alignment of an implant relative to the anatomicor biomechanical axis.

In another embodiment, standard tools including alignment guides may beattached to the mold, via linkages for example, and the attachment canallow for additional adjustments in mold and subsequently implantalignment and rotation.

The above-described embodiments can be particularly useful foroptimization of soft tissue tension including ligament balancing, forexample, in a knee joint. Optimization of soft tissue tension canadvantageously improve post-operative function and range of motion.

Linkages may also be utilized to stabilize and fix additional molds orsurgical instruments on the articular surface.

Moreover, linkages can allow separation of one large mold into multiplesmaller molds. The use of multiple smaller, linked molds advantageouslyenable smaller surgical axis with the potential to enhance musclesparing and to reduce the size of the skin cut.

In another embodiment, all or portions of the template may be made ofmetal, metal-alloys, teflon, ceramics. In a more preferred embodiment,metal, metal-alloys, teflon, ceramics and other hard materials,typically materials that offer a hardness of, without limitation,greater than shore 60D, is placed in areas where the surgicalinstruments will be in contact with the template.

ii. 3D Guidance Molds for Ligament Repair and Replacement

3D guidance molds may also be utilized for planning the approach andpreparing the surgical intervention and conducting the surgicalintervention for ligament repair and replacement, in accordance with anembodiment of the invention.

In one example, the anterior cruciate ligament is replaced using a 3Dguidance mold. The anterior cruciate ligament is a collagenous structurelocated in the center of the knee joint, and is covered by the synovialsheath. The ligament has an average length of thirty (30) tothirty-eight (38) millimeters and an average width of ten (10) to eleven(11) millimeters. The ligament is proximally attached to the posterioraspect of the lateral femoral condyle's medial surface. The ligamentpasses anteriorly, medially and distally within the joint to itsattachment at the anteromedial region of the tibial plateau, between thetibial eminences. The distal portion of the ligament fans out to createa large tibial attachment known as the footprint of the ligament. Theligament has two functional subdivisions which include the anteromedialband and the posterolateral band. The posterolateral band is taut whenthe knee is extended and the anteromedial band becomes taut when theknee is flexed. Because of its internal architecture and attachmentssides on femur and tibia, the ACL provides restraint to anteriortranslation and internal rotation of the tibia in angulation andhyperextension of the knee. The prevalence of ACL injuries are about 1in 3,000 subjects in the United States and approximately 250,000 newinjuries each year.

Other tendon and ligament injuries, for example, including the rotatorcuff, the ankle tendons and ligaments, or the posterior cruciateligament can also be highly prevalent and frequent.

Selecting the ideal osseous tunnel sights is a crucial step in ligamentreconstruction, for example, the anterior and posterior cruciateligament.

In the following paragraphs, embodiments will be described in detail asthey can be applied to the anterior cruciate ligament. However, clearlyall embodiments mentioned below and modifications thereof are applicableto other ligaments, including the posterior cruciate ligament and alsotendons such as tendons around the ankle joint or rotator cuff andshoulder joint.

Anterior Cruciate Ligament

The normal anterior cruciate ligament is composed of a large number offibers. Each fiber can have a different length, a different origin and adifferent insertion and is frequently under different tension during therange of motion of the knee joint. One of the limitations of today's ACLgraft is that they have parallel fibers. Thus, even with ideal selectionof the placement of the osseous tunnels, fibers of an ACL graft willundergo length and tension changes with range of motion. Therefore,today's ACL replacement cannot duplicate the original ligament. However,placing the center of the osseous tunnels at the most isometric points,maximizes the stability that can be obtained during motion and minimizeslater on graft wear and ultimately resultant failure.

In illustrative embodiments, 3D guidance templates may be selected anddesigned to enable highly accurate, reproducible and minimally invasivegraft tunnels in the femur and the tibia.

In one embodiment, imaging such as MRI is performed pre-operatively. Theimages can be utilized to identify the origin of the ligament and itsinsertion onto the opposing articular surface, in the case of ananterior cruciate ligament, the tibia. Once the estimated location ofthe origin and the footprint, i.e. the insertion of the ligament hasbeen identified, 3D guidance templates may be made to be applied tothese areas or their vicinity.

The 3D guidance templates may be made and shaped to the articularsurface, for example, adjacent to the intended tunnel location or theymay be shaped to bone or cartilage outside the weight bearing zone, forexample, in the intercondylar notch. A 3D guidance template for femoralor tibial tunnel placement for ACL repair may include blocks,attachments or linkages for reference points or guide aperture to guideand direct the direction and orientation of a drill, and optionally,also the drill depth. Optionally, the 3D guidance templates may behollow. The 3D guidance templates may be circular, semi-circular orellipsoid. The 3D guidance templates may have a central opening toaccommodate a drill.

In one embodiment, the 3D guidance template is placed on, over or nearthe intended femoral or tibial entry point and subsequently the drillhole. Once proper anatomic positioning has been achieved, the ligamenttunnel can be created. The 3D guidance template, its shape, position,and orientation, may be optimized to reflect the desired tunnel locationin the femur and the tibia, wherein the tunnel location, position,orientation and angulation is selected to achieve the best possiblefunctional results. Additional considerations in placing the femoral ortibial tunnel includes a sufficient distance to the cortical bone inorder to avoid failure or fracture of the tunnel.

Thus, optionally, the distance of the tunnel to the adjacent corticalbone and also other articular structures may optionally be factored intothe position, shape and orientation of the femoral or tibial 3D guidancetemplates in order to achieve the optimal compromise between optimalligament function and possible post-operative complications such asfailure of the tunnel.

In another embodiment, the imaging test may be utilized to determine theorigin and insertion of the ligament. This determination can beperformed on the basis of bony landmarks identified on the scan, e.g. aCT scan or MRI scan. Alternatively, this determination can be performedby identifying ligament remnants, for example, in the area of theligament origin and ligament attachment. By determining the origin andthe insertion of the ligament the intended graft length may be estimatedand measured. This measurement may be performed for different poseangles of the joint such as different degrees of flexion, extension,abduction, adduction, internal and external rotation.

In another embodiment, the imaging test may be utilized to identify theideal graft harvest site wherein the graft harvest site can optionallybe chosen to include sufficiently long ligament portion and underlyingbone block proximally and distally in order to fulfill the requirementfor graft length as measured earlier in the imaging test. An additional3D guidance template for the same 3D guidance templates, possibly withlinkages, may be utilized to harvest the ligament and bone from thedonor site in the case of an autograft. Optionally, 3D guidancetemplates may also be utilized or designed or shaped or selected toguide the extent of an optional notchplasty. This can include, forexample, the removal of osteophytes.

In the case of an ACL replacement, the 3D guidance templates may in thismanner optimize selection of femoral and tibial tunnel sites. Tunnelsites may even be optimized for different knee pose angles, i.e. jointpositions, and different range of motion. Selecting the properlypositioned femoral tunnel site ensures maximum post operative kneestability.

The intra-articular site of the tibial tunnel has less effect on changesin graft length but its position can be optimized using properplacement, position, and shape of 3D guidance templates to preventintercondular notch impingement.

Moreover, the 3D guidance templates may include an optional stop for thedrill, for example, to avoid damage to adjacent neurovascular bundles oradjacent articular structures, including the articular cartilage orother ligaments.

Optionally, the 3D guidance templates may also include a stop, forexample, for a drill in order to include the drill depth.

The direction and orientation of the tibial tunnel and also the femoraltunnel may be determined with use of the 3D guidance template, wherebyit will also include selection of an optimal tunnel orientation in orderto match graft length as measured pre-operatively with the tunnel lengthand the intra-articular length of the graft ligament.

In one embodiment, a tibial 3D guidance template is, for example,selected so that its opening is located immediately posterior to theanatomic center of the ACL tibial footprint. Anatomic landmarks may befactored into the design, shape, orientation, and position of the tibialguidance template, optionally. These include, without limitation, theanterior horn of the lateral meniscus, the medial tibial spine, theposterior cruciate ligament, and the anterior cruciate ligament stump.

The tunnel site may be located utilizing the 3D guidance template in theanterior posterior plane by extending a line in continuation with theinner edge of the anterior horn of the lateral meniscus. This plane willtypically be located six (6) to seven (7) millimeters anterior to theinterior border of the PCL. The position, shape and orientation of the3D guidance template will be typically so that the resultant tibialtunnel and the resultant location and orientation of the ACL graft, oncein place, may touch the lateral aspect of the PCL, but will notsignificantly deflect it. Similarly, the location of the tibial guidancetemplate and the resultant ligament tunnel and the resultant location ofthe ACL graft, once in place, may be chosen so that the graft willneither abrade nor impinge against the medial aspect of the lateralfemoral condyle or the roof of the intercondylar notch when the knee is,for example, in full extension. In this manner, highly accurate graftplacement is possible thereby avoiding the problems of impingement andsubsequent graft failure.

In another embodiment, the pre-operative scan can be evaluated todetermine the maximal possible graft length, for example, patella tendongraft. If there is concern that the maximal graft length is notsufficient for the intended ACL replacement, the tunnel location andorientation, specifically the exits from the femur or the tibia can bealtered and optimized in order to match the graft length with the tunnellength and intra-articular length.

In a preferred embodiment, the graft length is measured or simulatedpre-operatively, for example, by measuring the optimal graft length fordifferent flexion and extension angles. Using this approach, an optimalposition, shape, orientation and design of the 3D guidance template maybe derived at an optimal compromise between isometric graft placement,avoidance of impingement onto the PCL, and/or avoidance of impingementonto the femoral condyle, maximizing achievable graft lengths.

Intraoperatively, the femoral and/or tibial 3D guidance templates mayinclude adjustment means. These adjustment means can, for example, allowmovement of the template by one or two or more millimeters intervals inposterior or medial or lateral orientation, with resultant movement ofthe femoral or tibial tunnel. Additionally, intraoperative adjustmentmay also allow for rotation of the template, with resultant rotation ofthe resultant femoral or tibial tunnels.

A single template may be utilized to derive the femoral tunnel. A singletemplate may also be utilized to derive the tibial tunnel. More than onetemplate may be used on either side.

Optionally, the templates may include linkages, for example, forattaching additional measurement devices, guide wires, or other surgicalinstruments. Alignment guides including mechanical, electrical oroptical devices may be attached or incorporated in this manner.

In another embodiment, the opposite articular surface may be crossreferenced against a first articular surface. For example, in the caseof an ACL repair, the femoral tunnel may be prepared first using a 3Dguidance template, whereby the 3D guidance template helps determine theoptimal femoral tunnel position, location, orientation, diameter, andshape. The femoral guidance template may include a link inferiorly tothe tibia or an attachable linkage, wherein said link or said attachablelinkage may be utilized to determine the ideal articular entry point forthe tibial tunnel. In this manner, the tibial tunnel can be created inan anatomic environment and in mechanical cross reference with thefemoral tunnel. The reverse approach is possible, whereby the tibialtunnel is created first using the 3D guidance template with a link orlinkage to a subsequently created femoral tunnel. Creating the femoralor tibial tunnel in reference to each other advantageously helps reducethe difficulty in performing the ligament repair and also can improvethe accuracy of the surgery in select clinical situations.

In another embodiment, the template for ligament repair may includeoptional flanges or extenders. These flanges or extenders may have thefunction of tissue retractors. By having tissue retractor function, theintra-articular template for ligament repair can provide the surgeonwith a clearer entry to the intended site of surgical intervention andimprove visualization. Moreover, flanges or extenders originating fromor attached to the 3D guidance templates may also serve as tissueprotectors, for example, protecting the posterior cruciate ligament, thearticular cartilage, or other articular structures as well asextra-articular structures.

In another embodiment, an additional 3D guidance template or linkages toa first or second articular 3D guidance templates can be utilized toplace ligament attachment means, for example, interference crews.

If an allograft is chosen and the allograft length and optionally,dimensions are known pre-operatively, additional adjustments may be madeto the position, shape and orientation of the 3D guidance templates andadditional tunnels in order to match graft dimensions with tunneldimensions and graft length with intra-femoral tunnel length,intra-articular length and intra-tibial tunnel length. Optionally, thisadjustment and optimization can be performed for different pose anglesof the joint, e.g. different degrees of flexion or extension.

FIGS. 40A-C illustrate an exemplary use of 3D guidance templates forperforming ligament repair; in this case repair of the anterior cruciateligament (ACL). A 3D guidance template 4000 is placed in theintercondylar notch region 4005. At least one surface 4010 of thetemplate 4000 is a mirror image of at least portions of the notch 4005or the femur. The template 4000 may be optionally placed against thetrochlea and/or the femoral condyle (not shown). The mold 4000 includesan opening 4020 and, optionally, metal sleeves 4030, wherein theposition, location and orientation of the opening 4020 and/or the metalsleeves 4030 determine the position and orientation of the femoral grafttunnel 4040.

A tibial template 4050 may be used to determine the location andorientation of the tibial tunnel 4060. Specifically, an opening 4065within the tibial mold 4050 will determine the position, angle andorientation of the tibial tunnel 4060. The opening may include optionalmetal sleeves 4068. At least one surface 4070 of the tibial template4050 will substantially match the surface of the tibia 4075. Thetemplate may be matched to a tibial spine 4080 wherein the tibial spinecan help identify the correct position of the mold and help fix thetemplate in place during the surgical intervention. Of note, the sleeves4030 and 4068 may be made of other hard materials, e.g. ceramics. Thefemoral and/or tibial template may be optionally attached to the femoralor tibial articular surface during the procedure, for example usingK-wires or screws.

FIG. 40C shows a top view of the tibial plateau 4085. The PCL 4086 isseen as are the menisci 4087. The original site of ACL attachment 4090is shown. The intended tunnel site 4092 may be slightly posterior to theoriginal ACL attachment 4090. The template 4095 may placed over theintended graft tunnel 4092. The template will typically have a perimeterslightly greater than the intended tunnel site. The templates may allowfor attachments, linkages or handles.

PCL Repair

All of the embodiments described above may also be applied to PCL repairas well as the repair of other ligaments or tendons.

For PCL repair, 3D guidance templates may be designed for single, aswell as double bundle surgical technique. With single bundle surgicaltechnique, a 3D guidance template may be created with a position,orientation and shape of the template or associated reference points orguide apertures for surgical instruments that will help create a femoraltunnel in the location of the anatomic origin of the ligament.Alternatively, the template and any related reference points or guideapertures or linkages may be designed and placed so that an anteriorplacement of the femoral tunnel in the anatomic footprint is performed.A more anterior placement of the femoral tunnel can restore normal kneelaxity better than isometric graft placement. The 3D guidance templatesmay be designed so that optimal tension is achieved not only in kneeextension but also in knee flexion, particularly ninety degrees of kneeflexion. Thus, the origin and the insertion of the PCL may be identifiedpre-operatively on the scan, either by identifying residual fiberbundles or by identifying the underlying anatomic landmarks. Thedistance between the origin and the insertion may thus be determined inthe extension and can be simulated for different flexion degrees orother articular positions. Femoral and tibial tunnel placement andorientation may then be optimized in order to achieve an isometric ornear isometric ligament placement. Intraoperative adjustments arefeasible as described in the foregoing embodiments.

A 3D guidance template may also be designed both on the femoral as wellas on the tibial side using double bundle reconstruction techniques.With double bundle reconstruction techniques, the femoral or tibialtemplate can include or incorporate links or can have attachablelinkages so that a femoral tunnel can be created and cross referencedwith a tibial tunnel, or a tibial tunnel can be created and crossreferenced to a femoral tunnel.

As described for the ACL, the templates may include stops for drills andreaming devices or other surgical instruments, for example, to protectpopliteal neurovascular structures. The templates may include extendersor flanges to serve as tissue retractors as well as tissue protectors.

In principle, templates may be designed to be compatible with anydesired surgical technique. In the case of PCL repair, templates may bedesigned to be compatible with single bundle, or a double bundlereconstruction, tibial inlay techniques as well as other approaches.

As previously stated, 3D guidance templates are applicable to any typeof ligament or tendon repair and can provide reproducible, simpleintraoperative location of intended attachment sites or tunnels. Theshape, orientation and position of the 3D guidance templates may beindividualized and optimized for articular anatomy, as well as thebiomechanical situation, and may incorporate not only the articularshape but also anatomic lines, anatomic planes, biomechanical lines orbiomechanical planes, as well as portions or all of the shape of devicesor anchors or instruments to be implanted or to be used duringimplantation or to be used during surgical repair of a ligament ortendon tear.

iii. Impingement Syndromes, Removal of Exophytic Bone Growth IncludingOsteophytes

3D guidance templates may also be utilized to treat impingementsyndromes, for example, by template guided removal of osteophytes orexophytic bone growth. In one embodiment of the invention, an imagingtest such as a CT scan or an MRI scan is obtained through the area ofconcern. If a joint is imaged, the images can demonstrate an osteophyteor, more generally, exophytic bone growth in intra and extra-articularlocations. The scan data may then be utilized to design a template thatmatches the surface adjacent to the exophytic bone growth or osteophyte,the surface overlying the exophytic bone growth or osteophyte or both orportions of one or both. The template may have openings or apertures orlinkages that allow placement of surgical tools for removal of theexophytic bone growth or the osteophyte, such as reamers, drills,rotating blades and the like. Someone skilled in the art will recognizemany different surgical instruments that can be utilized in this manner.

Two representative examples where a 3D guidance template can be appliedto treat local impingement syndromes are the pincer and Cam impingementsyndromes in the hip joint. Pincer and Cam impingement representfemoro-acetabular impingement syndromes caused by an abutment betweenthe proximal femur and the acetabular rim during the end range ofmotion. Untreated femoral-acetabular impingement can causeosteoarthritis of the hip.

In Cam impingement, a non-spherical portion of the femoral head,typically located near the head-neck junction, is jammed into theacetabulum during hip joint motion. The Cam impingement can lead toconsiderable shear forces and subsequently chondral erosion.

In one embodiment of the invention, an imaging test, such as a CT scanor MRI scan may be performed pre-operatively. The imaging test may beused to identify the non-spherical portion of the femoral head at thehead-neck junction that is responsible for the impingement. A 3Dguidance template may be designed that can be applied intraoperativelyto this region. The template is designed to fulfill three principlefunctions:

1. Intraoperative highly accurate identification of the non-sphericalportion of the femoral head by placement of the individualized portionof the 3D template onto the area or immediately adjacent to the area.

2. Guidance of surgical instrumentation to remove the non-sphericalportion and to re-establish a spherical or essentially spherical shape.

3. Control of the depth of the bone removal and the shape of the boneremoval. For this purpose, a stop may be incorporated into the design ofthe 3D guidance template. Of note, the stop may be asymmetrical and caneven be designed to be a mirror image of the desired articular contour.

FIG. 41 shows an example of treatment of CAM impingement using a 3Dguidance template 4100. The impinging area 4105 may be removed with asaw (not shown) inserted into the guide aperture 4110. The guideaperture may be designed and placed so that only the impinging portionof the joint is removed.

In Pincer impingement, linear bony contact occurs between the normalfemoral head-neck junction and enlarged or hypertrophied portion of theacetabulum. Pre-operatively an imaging test may be performed in order toidentify the abnormal, over covered or enlarged area of the acetabulum.The amount of bone removal may be determined on the imaging study, e.g.a CT scan or MRI scan. A 3D guidance template may then be designed thatwill achieve the identical three functions described above in Camimpingement.

FIG. 42 shows an example of treatment of Pincer impingement using a 3Dguidance template 4200. The impinging area 4205 may be removed with asaw (not shown) inserted into the guide aperture 4210. The guideaperture may be designed and placed so that only the impinging portionof the joint is removed.

Accurate and reproducible identification of the abnormal bony surfacecausing the impingement is critical in any form of musculoskeletalimpingement syndrome. 3D guidance template systems are ideally suited toachieve this purpose and to guide the surgical instrumentation forremoval of the source of impingement. Moreover, since the localizationof the impinging area is performed pre-operatively during the imagingtest, and intra-operatively using the 3D guidance template, thisapproach allows for minimally invasive, tissue, specifically musclesparing approaches.

iv. Surgical Navigation and 3D Guidance Templates

3D guidance template technology as described herein may be combined withsurgical navigation techniques. Surgical navigation techniques may beimage guided or non-image guided for this purpose. Passive or activesurgical navigation systems may be employed. Surgical navigation systemsthat use optical or radiofrequency transmission or registration may beused. A representative example is the Vector Vision navigation systemmanufactured by Brain Lab, Germany. This is a passive infrarednavigation system. Once the patient is positioned appropriately in theoperating room, retro-reflective markers can be applied to the extremitynear the area of intended surgery. With image guided navigation, animaging study such as a CT scan or MRI scan, can be transferred into theworkstation of the navigation system. For registration purposes, thesurgeon can, for example, utilize a pointer navigation tool to touchfour or more reference points that are simultaneously co-identified andcross registered on the CT or MRI scan on the workstation. In the kneejoint, reference points may include the trochlear groove, the mostlateral point of the lateral condyle, the most medial femoral condyle,the tip of the tibial spines and so forth. Using image guidednavigation, anatomical and biomechanical axis of the joint can bedetermined reliably.

Alternatively, non-image guided navigation may be utilized. In thiscase, retro-reflective markers or small radio frequency transmitters arepositioned on the extremity. Movement of the extremity and of the jointsis utilized, for example, to identify the center of rotation. If surgeryof the knee joint is contemplated, the knee joint may be rotated aroundthe femur. The marker or radiofrequency transmitter motion may beutilized to identify the center of the rotation, which will coincidewith the center of the femoral head. In this manner, the biomechanicalaxis may be determined non-invasively.

The information resulting in imaging guided navigation, pertaining toeither anatomical or biomechanical axis can be may be utilized tooptimize the position of any molds, blocks, linkages or surgicalinstruments attached to or guided through the 3D guidance molds.

In one embodiment, the joint or more specifically the articular surface,may be scanned intra-operatively, for example, using ultrasound oroptical imaging methods. The optical imaging methods may includestereographic or stereographic like imaging approaches, for example,multiple light path stereographic imaging of the joint and the articularsurface or even single light path 3D optical imaging. Other scantechnologies that are applicable are, for example, C-arm mountedfluoroscopic imaging systems that can optionally also be utilized togenerate cross-sectional images such as a CT scan. Intraoperative CTscanners are also applicable. Utilizing the intraoperative scan, a pointcloud of the joint or the articular surface or a 3D reconstruction or a3D visualization and other 3D representations may be generated that canbe utilized to generate an individualized template wherein at least aportion of said template includes a surface that is a mirror image ofthe joint or the articular surface. A rapid prototyping or a milling orother manufacturing machine can be available in or near the operatingroom and the 3D guidance template may be generated intraoperatively.

The intraoperative scan in conjunction with the rapid production of anindividualized 3D guidance template matching the joint or the articularsurface, in whole or at least in part, has the advantage to generaterapidly a tool for rapid intraoperative localization of anatomicallandmarks, including articular landmarks. A 3D guidance template maythen optionally be cross-registered, for example, using optical markersor radiofrequency transmitters attached to the template with thesurgical navigation system. By cross-referencing the 3D guidancetemplate with the surgical navigation system, surgical instruments cannow be reproducibly positioned in relationship to the 3D guidancetemplate to perform subsequent procedures in alignment with or in adefined relationship to at least one or more anatomical axis and/or atleast one or more biomechanical axis or planes.

v. Stereoscopy, Stereoscopic Imaging:

In addition to cross-sectional or volumetric imaging technologiesincluding CT, spiral CT, and MRI, stereoscopic imaging modalities may beutilized. Stereoscopic imaging is any technique capable of recordingthree-dimensional information from two two-dimensional, projectionalimaging. Traditional stereoscopic imaging includes creating a 3Dvisualization or representation starting from a pair of 2D images. Theprojection path of the 2D images is offset. The offset is, for example,designed to create an impression of object depth for the eyes of theviewer. The offset or minor deviation between the two images is similarto the prospectors that both eyes naturally receive inbinocular vision.Using two or more images with an offset or minor deviation inperspective, it is possible to generate a point cloud or 3D surface or3D visualization of a joint or an articular surface, which can then beinput into a manufacturing system such as a rapid prototyping or millingmachine. Dual or more light path, as well as single light path, systemscan be employed

vi. Knee Joint

When a total knee arthroplasty is contemplated, the patient can undergoan imaging test, as discussed in more detail above, that willdemonstrate the articular anatomy of a knee joint, e.g. width of thefemoral condyles, the tibial plateau etc. Additionally, other joints canbe included in the imaging test thereby yielding information on femoraland tibial axes, deformities such as varus and valgus and otherarticular alignment. The imaging test can be an x-ray image, preferablyin standing, load-bearing position, a CT or spiral CT scan or an MRIscan or combinations thereof. A spiral CT scan may be advantageous overa standard CT scan due to its improved spatial resolution in z-directionin addition to x and y resolution. The articular surface and shape aswell as alignment information generated with the imaging test can beused to shape the surgical assistance device, to select the surgicalassistance device from a library of different devices with pre-madeshapes and sizes, or can be entered into the surgical assistance deviceand can be used to define the preferred location and orientation of sawguides or drill holes or guides for reaming devices or other surgicalinstruments. Intraoperatively, the surgical assistance device is appliedto the tibial plateau and subsequently the femoral condyle(s) bymatching its surface with the articular surface or by attaching it toanatomic reference points on the bone or cartilage. The surgeon can thenintroduce a reamer or saw through the guides and prepare the joint forthe implantation. By cutting the cartilage and bone along anatomicallydefined planes, a more reproducible placement of the implant can beachieved. This can ultimately result in improved postoperative resultsby optimizing biomechanical stresses applied to the implant andsurrounding bone for the patient's anatomy and by minimizing axismalalignment of the implant. In addition, the surgical assistance devicecan greatly reduce the number of surgical instruments needed for totalor unicompartmental knee arthroplasty. Thus, the use of one or moresurgical assistance devices can help make joint arthroplasty moreaccurate, improve postoperative results, improve long-term implantsurvival, reduce cost by reducing the number of surgical instrumentsused. Moreover, the use of one or more surgical assistance device canhelp lower the technical difficulty of the procedure and can helpdecrease operating room (“OR”) times.

Thus, surgical tools described herein can also be designed and used tocontrol drill alignment, depth and width, for example when preparing asite to receive an implant. For example, the tools described herein,which typically conform to the joint surface, can provide for improveddrill alignment and more accurate placement of any implant. Ananatomically correct tool can be constructed by a number of methods andcan be made of any material, preferably a substantially translucentand/or transparent material such as plastic, Lucite, silastic, SLA orthe like, and typically is a block-like shape prior to molding.

FIG. 24A depicts, in cross-section, an example of a mold 600 for use onthe tibial surface having an upper surface 620. The mold 600 contains anaperture 625 through which a surgical drill or saw can fit. The apertureguides the drill or saw to make the proper hole or cut in the underlyingbone 610 as illustrated in FIGS. 21B-D. Dotted lines 632 illustratewhere the cut corresponding to the aperture will be made in bone.

FIG. 24B depicts, a mold 608 suitable for use on the femur. As can beappreciated from this perspective, additional apertures are provided toenable additional cuts to the bone surface. The apertures 605 enablecuts 606 to the surface of the femur. The resulting shape of the femurcorresponds to the shape of the interior surface of the femoral implant,typically as shown in FIG. 21E. Additional shapes can be achieved, ifdesired, by changing the size, orientation and placement of theapertures. Such changes would be desired where, for example, theinterior shape of the femoral component of the implant requires adifferent shape of the prepared femur surface.

Turning now to FIG. 25, a variety of illustrations are provided showinga tibial cutting block and mold system. FIG. 25A illustrates the tibialcutting block 2300 in conjunction with a tibia 2302 that has not beenresected. In this depiction, the cutting block 2300 consists of at leasttwo pieces. The first piece is a patient specific interior piece 2310 ormold that is designed on its inferior surface 2312 to mate, orsubstantially mate, with the existing geography of the patient's tibia2302. The superior surface 2314 and side surfaces 2316 of the firstpiece 2310 are configured to mate within the interior of an exteriorpiece 2320. The reusable exterior piece 2320 fits over the interiorpiece 2310. The system can be configured to hold the mold onto the bone.

The reusable exterior piece has a superior surface 2322 and an inferiorsurface 2324 that mates with the first piece 2310. The reusable exteriorpiece 2320 includes cutting guides 2328, to assist the surgeon inperforming the tibial surface cut described above. As shown herein aplurality of cutting guides can be provided to provide the surgeon avariety of locations to choose from in making the tibial cut. Ifnecessary, additional spacers can be provided that fit between the firstpatient configured, or molded, piece 2310 and the second reusableexterior piece, or cutting block, 2320.

Clearly, the mold may be a single component or multiple components. In apreferred embodiment, one or more components are patient specific whileother components such as spacers or connectors to surgical instrumentsare generic. In one embodiment, the mold can rest on portions of thejoint on the articular surface or external to the articular surface.Other surgical tools then may connect to the mold. For example, astandard surgical cut block as described for standard implants, forexample in the knee the J&J PFC Sigma system, the Zimmer Nexgen systemor the Stryker Duracon system, can be connected or placed on the mold.In this manner, the patient specific component can be minimized and canbe made compatible with standard surgical instruments.

The mold may include receptacles for standard surgical instrumentsincluding alignment tools or guides. For example, a tibial mold for usein knee surgery may have an extender or a receptacle or an opening toreceive a tibial alignment rod. In this manner, the position of the moldcan be checked against the standard alignment tools and methods.Moreover, the combined use of molds and standard alignment toolsincluding also surgical navigation techniques can help improve theaccuracy of or optimize component placement in joint arthroplasty, suchas hip or knee arthroplasty. For example, the mold can help define thedepth of a horizontal tibial cut for placement of a tibial component. Atibial alignment guide, for example an extramedullary or intramedullaryalignment guide, used in conjunction with a tibial mold can help findthe optimal anteroposterior angulation, posterior slope, tibial slant,or varus-valgus angle of the tibial cut. The mold may be designed towork in conjunction with traditional alignment tools known in the art.

The mold may include markers, e.g. optoelectronic or radiofrequency, forsurgical navigation. The mold may have receptacles to which such markerscan be attached, either directly or via a linking member.

The molds can be used in combination with a surgical navigation system.They can be used to register the bones associated with a joint into thecoordinate system of the surgical navigation system. For example, if amold for a joint surface includes tracking markers for surgicalnavigation, the exact position and orientation of the bone can bedetected by the surgical navigation system after placement of the moldin its unique position. This helps to avoid the time-consuming need toacquire the coordinates of tens to hundreds of points on the jointsurface for registration.

Referring back to FIG. 25, the variable nature of the interior piecefacilitates obtaining the most accurate cut despite the level of diseaseof the joint because it positions the exterior piece 2320 such that itcan achieve a cut that is perpendicular to the mechanical axis. Eitherthe interior piece 2310 or the exterior piece 2320 can be formed out ofany of the materials discussed above in Section II, or any othersuitable material. Additionally, a person of skill in the art willappreciate that the invention is not limited to the two piececonfiguration described herein. The reusable exterior piece 2320 and thepatient specific interior piece 2310 can be a single piece that iseither patient specific (where manufacturing costs of materials supportsuch a product) or is reusable based on a library of substantiallydefect conforming shapes developed in response to known or common tibialsurface sizes and defects.

The interior piece 2310 is typically molded to the tibia including thesubchondral bone and/or the cartilage. The surgeon will typically removeany residual meniscal tissue prior to applying the mold. Optionally, theinterior surface 2312 of the mold can include shape information ofportions or all of the menisci.

Turning now to FIG. 25B-D, a variety of views of the removable exteriorpiece 2320. The top surface 2322 of the exterior piece can be relativelyflat. The lower surface 2324 which abuts the interior piece conforms tothe shape of the upper surface of the interior piece. In thisillustration the upper surface of the interior piece is flat, thereforethe lower surface 2324 of the reusable exterior surface is also flat toprovide an optimal mating surface.

A guide plate 2326 is provided that extends along the side of at least aportion of the exterior piece 2320. The guide plate 2326 provides one ormore slots or guides 2328 through which a saw blade can be inserted toachieve the cut desired of the tibial surface. Additionally, the slot,or guide, can be configured so that the saw blade cuts at a lineperpendicular to the mechanical axis, or so that it cuts at a line thatis perpendicular to the mechanical axis, but has a 4-7° slope in thesagittal plane to match the normal slope of the tibia.

Optionally, a central bore 2330 can be provided that, for example,enables a drill to ream a hole into the bone for the stem of the tibialcomponent of the knee implant.

FIGS. 25E-H illustrate the interior, patient specific, piece 2310 from avariety of perspectives. FIG. 25E shows a side view of the piece showingthe uniform superior surface 2314 and the uniform side surfaces 2316along with the irregular inferior surface 2316. The inferior surfacemates with the irregular surface of the tibia 2302. FIG. 25F illustratesa superior view of the interior, patient, specific piece of the mold2310. Optionally having an aperture 2330. FIG. 25G illustrates aninferior view of the interior patient specific mold piece 2310 furtherillustrating the irregular surface which includes convex and concaveportions to the surface, as necessary to achieve optimal mating with thesurface of the tibia. FIG. 25H illustrates cross-sectional views of theinterior patient specific mold piece 2310. As can be seen in thecross-sections, the surface of the interior surface changes along itslength.

As is evident from the views shown in FIGS. 25B and D, the length of theguide plate 2326 can be such that it extends along all or part of thetibial plateau, e.g. where the guide plate 2326 is asymmetricallypositioned as shown in FIG. 25B or symmetrical as in FIG. 23D. If totalknee arthroplasty is contemplated, the length of the guide plate 2326typically extends along all of the tibial plateau. If unicompartmentalarthroplasty is contemplated, the length of the guide plate typicallyextends along the length of the compartment that the surgeon willoperate on. Similarly, if total knee arthroplasty is contemplated, thelength of the molded, interior piece 2310 typically extends along all ofthe tibial plateau; it can include one or both tibial spines. Ifunicompartmental arthroplasty is contemplated, the length of the moldedinterior piece typically extends along the length of the compartmentthat the surgeon will operate on; it can optionally include a tibialspine.

Turning now to FIG. 25I, an alternative embodiment is depicted of theaperture 2330. In this embodiment, the aperture features lateralprotrusions to accommodate using a reamer or punch to create an openingin the bone that accepts a stem having flanges.

FIGS. 25J and M depict alternative embodiments of the invention designedto control the movement and rotation of the cutting block 2320 relativeto the mold 2310. As shown in FIG. 25J a series of protrusions,illustrated as pegs 2340, are provided that extend from the superiorsurface of the mold. As will be appreciated by those of skill in theart, one or more pegs or protrusions can be used without departing fromthe scope of the invention. For purposes of illustration, two pegs havebeen shown in FIG. 25J. Depending on the control desired, the pegs 2340are configured to fit within, for example, a curved slot 2342 thatenables rotational adjustment as illustrated in FIG. 23K or within arecess 2344 that conforms in shape to the peg 2340 as shown in FIG. 25L.As will be appreciated by those of skill in the art, the recess 2344 canbe sized to snugly encompass the peg or can be sized larger than the pegto allow limited lateral and rotational movement. The recess can becomposed of a metal or other hard insert 544.

As illustrated in FIG. 25M the surface of the mold 2310 can beconfigured such that the upper surface forms a convex dome 2350 thatfits within a concave well 2352 provided on the interior surface of thecutting block 2320. This configuration enables greater rotationalmovement about the mechanical axis while limiting lateral movement ortranslation.

Other embodiments and configurations could be used to achieve theseresults without departing from the scope of the invention.

As will be appreciated by those of skill in the art, more than twopieces can be used, where appropriate, to comprise the system. Forexample, the patient specific interior piece 2310 can be two pieces thatare configured to form a single piece when placed on the tibia.Additionally, the exterior piece 2320 can be two components. The firstcomponent can have, for example, the cutting guide apertures 2328. Afterthe resection using the cutting guide aperture 2328 is made, theexterior piece 2320 can be removed and a secondary exterior piece 2320′can be used which does not have the guide plate 2326 with the cuttingguide apertures 2328, but has the aperture 2330 which facilitates boringinto the tibial surface an aperture to receive a stem of the tibialcomponent of the knee implant. Any of these designs could also featurethe surface configurations shown in FIGS. 25J-M, if desired.

FIG. 25N illustrates an alternative design of the cutting block 2320that provides additional structures 2360 to protect, for example, thecruciate ligaments, from being cut during the preparation of the tibialplateau. These additional structures can be in the form of indentedguides 2360, as shown in FIG. 25N or other suitable structures.

FIG. 25O illustrates a cross-section of a system having anchoring pegs2362 on the surface of the interior piece 2310 that anchor the interiorpiece 2310 into the cartilage or meniscal area.

FIGS. 25P AND Q illustrate a device 2300 configured to cover half of atibial plateau such that it is unicompartmental.

FIG. 25R illustrates an interior piece 2310 that has multiple contactsurfaces 2312 with the tibial 2302, in accordance with one embodiment ofthe invention. As opposed to one large contact surface, the interiorpiece 2310 includes a plurality of smaller contact surfaces 2312. Invarious embodiments, the multiple contact surfaces 2312 are not on thesample plane and are at angles relative to each other to ensure properpositioning on the tibia 2302. Two or three contact surfaces 2312 may berequired to ensure proper positioning. In various embodiments, only thecontact surfaces 2312 of the interior piece may be molded, the moldsattached to the rest of the template using methodologies known in theart, such as adhesives. The molds may be removably attached to thetemplate. It is to be understood that multiple contact surfaces 2312 maybe utilized in template embodiments that include one or a plurality ofpieces.

Turning now to FIG. 26, a femoral mold system is depicted thatfacilitates preparing the surface of the femur such that the finallyimplanted femoral implant will achieve optimal mechanical and anatomicalaxis alignment.

FIG. 26A illustrates the femur 2400 with a first portion 2410 of themold placed thereon. In this depiction, the top surface of the mold 2412is provided with a plurality of apertures. In this instance theapertures consist of a pair of rectangular apertures 2414, a pair ofsquare apertures 2416, a central bore aperture 2418 and a longrectangular aperture 2420. The side surface 2422 of the first portion2410 also has a rectangular aperture 2424. Each of the apertures islarger than the eventual cuts to be made on the femur so that, in theevent the material the first portion of the mold is manufactured from asoft material, such as plastic, it will not be inadvertently cut duringthe joint surface preparation process. Additionally, the shapes can beadjusted, e.g., rectangular shapes made trapezoidal, to give a greaterflexibility to the cut length along one area, without increasingflexibility in another area. As will be appreciated by those of skill inthe art, other shapes for the apertures, or orifices, can be changedwithout departing from the scope of the invention.

FIG. 26B illustrates a side view of the first portion 2410 from theperspective of the side surface 2422 illustrating the aperture 2424. Asillustrated, the exterior surface 2411 has a uniform surface which isflat, or relatively flat configuration while the interior surface 2413has an irregular surface that conforms, or substantially conforms, withthe surface of the femur.

FIG. 26C illustrates another side view of the first, patient specificmolded, portion 2410, more particularly illustrating the irregularsurface 2413 of the interior. FIG. 26D illustrates the first portion2410 from a top view. The center bore aperture 2418 is optionallyprovided to facilitate positioning the first piece and to preventcentral rotation.

FIG. 26D illustrates a top view of the first portion 2410. The bottom ofthe illustration corresponds to an anterior location relative to theknee joint. From the top view, each of the apertures is illustrated asdescribed above. As will be appreciated by those of skill in the art,the apertures can be shaped differently without departing from the scopeof the invention.

Turning now to FIG. 26E, the femur 2400 with a first portion 2410 of thecutting block placed on the femur and a second, exterior, portion 2440placed over the first portion 2410 is illustrated. The second, exterior,portion 2440 features a series of rectangular grooves (2442-2450) thatfacilitate inserting a saw blade therethrough to make the cuts necessaryto achieve the femur shape illustrated in FIG. 21E. These grooves canenable the blade to access at a 90° angle to the surface of the exteriorportion, or, for example, at a 45° angle. Other angles are also possiblewithout departing from the scope of the invention.

As shown by the dashed lines, the grooves (2442-2450) of the secondportion 2440, overlay the apertures of the first layer.

FIG. 26F illustrates a side view of the second, exterior, cutting blockportion 2440. From the side view a single aperture 2450 is provided toaccess the femur cut. FIG. 26G is another side view of the second,exterior, portion 2440 showing the location and relative angles of therectangular grooves. As evidenced from this view, the orientation of thegrooves 2442, 2448 and 2450 is perpendicular to at least one surface ofthe second, exterior, portion 2440. The orientation of the grooves 2444,2446 is at an angle that is not perpendicular to at least one surface ofthe second, exterior portion 2440. These grooves (2444, 2446) facilitatemaking the angled chamfer cuts to the femur. FIG. 26H is a top view ofthe second, exterior portion 2440. As will be appreciated by those ofskill in the art, the location and orientation of the grooves willchange depending upon the design of the femoral implant and the shaperequired of the femur to communicate with the implant.

FIG. 26I illustrates a spacer 2401 for use between the first portion2410 and the second portion 2440. The spacer 2401 raises the secondportion relative to the first portion, thus raising the area at whichthe cut through groove 2424 is made relative to the surface of thefemur. As will be appreciated by those of skill in the art, more thanone spacer can be employed without departing from the scope of theinvention. Spacers can also be used for making the tibial cuts. Optionalgrooves or channels 2403 can be provided to accommodate, for example,pins 2460 shown in FIG. 26J.

Similar to the designs discussed above with respect to FIG. 25,alternative designs can be used to control the movement and rotation ofthe cutting block 2440 relative to the mold 2410. As shown in FIG. 26J aseries of protrusions, illustrated as pegs 2460, are provided thatextend from the superior surface of the mold. These pegs or protrusionscan be telescoping to facilitate the use of molds if necessary. As willbe appreciated by those of skill in the art, one or more pegs orprotrusions can be used without departing from the scope of theinvention. For purposes of illustration, two pegs have been shown inFIG. 26J. Depending on the control desired, the pegs 2460 are configuredto fit within, for example, a curved slot that enables rotationaladjustment similar to the slots illustrated in FIG. 25K or within arecess that conforms in shape to the peg, similar to that shown in FIG.25L and described with respect to the tibial cutting system. As will beappreciated by those of skill in the art, the recess 2462 can be sizedto snugly encompass the peg or can be sized larger than the peg to allowlimited lateral and rotational movement.

As illustrated in FIG. 26K the surface of the mold 2410 can beconfigured such that the upper surface forms a convex dome 2464 thatfits within a concave well 2466 provided on the interior surface of thecutting block 2440. This configuration enables greater rotationalmovement about the mechanical axis while limiting lateral movement ortranslation.

In installing an implant, first the tibial surface is cut using a tibialblock, such as those shown in FIG. 26. The patient specific mold isplaced on the femur. The knee is then placed in extension and spacers2401, such as those shown in FIG. 26M, or shims are used, if required,until the joint optimal function is achieved in both extension andflexion. The spacers, or shims, are typically of an incremental size,e.g., 5 mm thick to provide increasing distance as the leg is placed inextension and flexion. A tensiometer can be used to assist in thisdetermination or can be incorporated into the mold or spacers in orderto provide optimal results. The design of tensiometers are known in theart and are not included herein to avoid obscuring the invention.Suitable designs include, for example, those described in U.S. Pat. No.5,630,820 to Todd issued May 20, 1997.

As illustrated in FIGS. 26N (sagittal view) and 26O (coronal view), theinterior surface 2413 of the mold 2410 can include small teeth 2465 orextensions that can help stabilize the mold against the cartilage 2466or subchondral bone 2467.

3D guidance templates may be used to create more that one cut on thesame and/or on the opposite articular surface or opposite articularbone, in accordance with an embodiment of the invention. These cuts maybe cross-referenced with other cuts using one or more guidancetemplate(s).

In accordance with one embodiment of the invention, the 3D guidancetemplate(s) are utilized to perform more than one cut on the samearticular side such as the femoral side of a knee joint. In anotherembodiment, a 3D guidance template may be utilized to cross referencesurgical interventions on an opposing articular surface. In a knee, forexample, the first articular surface can be the femoral surface. Theopposing articular surface can be the tibial surface or the patellasurface. In a hip, the first articular surface can be the acetabulum.The opposing articular surface or the opposing bone can be the proximalfemur.

Thus, in a knee, a horizontal femur cut can be cross-referenced with ananterior or posterior femur cut or optionally also chamfer, obliquecuts. Similarly, a tibial horizontal cut can be cross-referenced withany tibial oblique or vertical cuts on the same articular side orsurface.

In accordance with another embodiment, one or more femur cuts can becrossed-referenced with one or more tibial cuts. Or, in a hip, one ormore acetabular cuts or surgical interventions can be cross-referencedwith one or more femoral cuts or surgical interventions such asdrilling, reaming or boring. Similarly, in a knee again, one or morefemur cuts can be cross-referenced with one or more patella cuts. Anycombination and order is possible.

The cross-referencing can occur via attachments or linkages includingspacers or hinge or ratchet like devices from a first articular boneand/or cartilage surface, to a second articular, bone and/or cartilagesurface. The resulting positioning of the cut on the opposing articular,bone or cartilage surface can be optimized by testing the cut formultiple pose angles or joint positions such as flexion, extension,internal or external rotation, abduction or adduction. Thus, forexample, in a knee a distal femur cut can be performed with a mold. Viaa linkage or an attachment, a tibial template may be attached thereto orto the cut or other surgical intervention, thus a cross-reference can berelated from the femoral cut to a tibial cut or other surgicalintervention. Cross-referencing from a first articular surface to asecond articular surface via, without limitation, attachments orlinkages to a template has the advantage of insuring an optimalalignment between the implant or other therapeutic device components ofthe first articular surface to that on a second articular surface.Moreover, by cross-referencing surgical interventions on a firstarticular surface to a second articular surface, improved efficienciesand time savings can be obtained with the resulted surgical procedure.

Cross-referencing the first, the second and, optionally a third or morearticular surface, such as in a knee joint, may be performed with asingle linkage or attachment or multiple linkages or attachments. Asingle pose angle or position of a joint or multiple pose angles orpositions of a joint may be tested and optimized during the entiresurgical intervention. Moreover, any resulting surgical interventions onthe opposite, second articular surface, bone or cartilage may be furtheroptimized by optionally cross-referencing to additional measurementtools such as standard alignment guides.

For example, in a knee joint, a 3D template may be utilized to performone or more surgical interventions on the femoral side, such as afemoral cut. This can then be utilized via a linkage, an attachment orvia indirect cross-referencing directly onto the site of surgicalintervention, to guide a surgical intervention such as a cut of thetibial side. Prior to performing the surgical intervention on the tibialside, a traditional tibial alignment guide with cross-reference to themedial and lateral malleolus of the ankle turn may be used to optimizethe position, orientation and/or depth and extent of the plannedsurgical intervention such as the cut. For example, cross-referencing tothe femoral cut can aid in defining the relative superior inferiorheight of the tibial cut, while cross-referencing a tibial alignmentguide can optionally be utilized to determine the slant of the cut inthe interior posterior direction.

An exemplary system and methodology is now described in which a femoraltemplate is used to make a cut on the femur, which is thencross-referenced to properly align a tibial template for making a cut onthe tibial plateau. Initially, an electronic image(s) of the leg isobtained using imaging techniques elaborated in above-describedembodiments. For example, a pre-operative CT scan of a patient's leg maybe obtained to obtain electronic image data.

Image processing is then applied to the image data to derive, withoutlimitation, relevant joint surfaces, axis, and/or cut planes. Imageprocessing techniques may include, without limitation, segmentation andpropagation of point clouds.

Relevant biomechanical and/or anatomical axis data may be obtained byidentifying, for example, the central femoral head, central knee jointand center of the distal tibia. The cutting planes may then be definedbased on at least one of these axis. For example, the tibial implantbearing surface may be defined as being perpendicular to the axisdefined by the center of the tibial plateau 2496 and the center of thedistal tibia 2497, as illustrated in FIG. 26P; the tibial implant'smedial margin may project towards the femoral head, as illustrated inFIG. 26Q; and the anterior to posterior slope of the tibia may beapproximated by the natural anatomical slope (alternatively, excessivetibial slope may be corrected).

The tibial and femoral templates and implants may be designed based, atleast in part, on the derived joint surfaces, axis and/or cut planes.FIGS. 26R and 26S show isometric views of a femoral template 2470 and atibial template 2480, respectively, in accordance with an embodiment ofthe invention. The femoral template 2470 has an interior surface that,in various embodiments, conforms, or substantially conforms, with theanatomic surface (bone and/or cartilage) of the femur 2475. Furthermore,the interior surface of the femoral template may extend a desired amountaround the anatomical boney surfaces of the condyle to further ensureproper fixation. The interior surface of the tibial cutting block 2480may conform, or substantially conform to the surface (bone and/orcartilage) of the tibia 2481.

In an exemplary use, the femoral template 2470 is placed on the femoralcondyle 2475, for example, when the knee is flexed. The femoral template2470 may be fixed to the femoral condyle 2475 using, without limitation,anchoring screws/drill pins inserted through drill bushing holes 2471and 2472. The position of holes 2471 and 2472 on the condyle may be thesame used to anchor the final implant to the femur. In variousembodiments, the holes 2471 and 2472 may include metal inserts/bushingsto prevent degradation when drilling. Fixing the template 2470 to thefemoral condyle 2475 advantageously prevents movement of the templateduring subsequent cutting or other surgical interventions therebyensuring the accuracy of the resultant surgical cuts.

To assist in accurately positioning the femoral template 2470, a femoralguide reference tool 2473 may be attached to the femoral template 2470,as shown in FIG. 26T. The femoral guide reference tool 2473 may, withoutlimitation, attach to one of holes 2471 and 2472. The femoral guidereference tool 2473 may reference off the tangential margin of theposterior condyle, and aid, for example, in correct anterior-posteriorpositioning of the femoral template 2470.

Upon proper fixation of the femoral template 2470 to the femoral condyle2475, a cut to the femoral condyle is made using cut guide surface orelement 2474. The cut guide surface or element 2474 may be integral tothe femoral template 2470, or may be an attachment to the femoraltemplate 2470, with the attachment made of a harder material than thefemoral template 2470. For example, the cut guide surface or element2474 may be a metal tab that slides onto the femoral template 2470,which may be made, without limitation, of a softer, plastic material.

Upon making the femoral cut and removing the femoral template 2475, asample implant template 2476 (not the final implant) is optionallypositioned on the condyle, as shown in FIG. 26U, in accordance with anembodiment of the invention. The sample implant template 2474 may beattached to the condyle by using without limitation, anchoringscrews/drill pins inserted through the same holes used to anchor thefinal implant to the femur.

The sample implant template 2476 includes an attachment mechanism 2494for attaching the tibial template 2480, thereby cross-referencing theplacement of the distal tibial cut with respect to the femoralcut/implant's placement. The attachment mechanism 2494 may be, withoutlimitation, a boss, as shown in FIG. 26U, or other attachment mechanismknown in the art, such as a snap-fit mechanism. Note that in alternativeembodiments, a sample implant template 2476 is not required. Forexample, the tibial template 2480 may attach directly to the femoraltemplate 2470. However, in the subject embodiment, the drill bushingfeatures of the femoral template 2475 will interfere with the knee goinginto extension, preventing the tibial cut.

In illustrative embodiments, the thickness of the sample implanttemplate 2476 may not only include the thickness of the final femoralimplant, but may include an additional thickness that corresponds to apreferred joint space between tibial and femoral implants. For example,the additional thickness may advantageously provide a desired jointspace identified for proper ligament balancing or for flexion,extension, rotation, abduction, adduction, anteversion, retroversion andother joint or bone positions and motion.

FIG. 26V is an isometric view of the interior surface of the sampleimplant template 2476, in accordance with an embodiment of theinvention. In various embodiments, the femoral implant often rests onsubchondral bone, with the cartilage being excised. In embodiments wherethe sample implant template 2474 extends beyond the dimensions of thefemoral implant such that portions of the sample implant template 2476rests on cartilage, an offset 2477 in the interior surface of the sampleimplant template 2476 may be provided.

FIG. 26W is an isometric view of the tibial template 2480 attached tothe sample implant 2476 when the knee is in extension, in accordancewith an embodiment of the invention. A crosspin 2478 inserted throughboss 2494 fixes the tibial template 2480 to the sample implant template2474. Of course, other attachment mechanisms may be used, as describedabove. In preferred embodiments, the tibial template 2480 may also befixed to the tibia 2481 using, without limitation, anchoringscrews/drill pins inserted through drill bushing hole 2479. In variousembodiments, the holes 2479 include metal inserts (or other hardmaterial) to prevent degradation when drilling. As with the femoraltemplate 2475, the cut guide surface or element of the tibial template2480 may be integral to the tibial template 2475, or may be anattachment to the tibial template 2480, the attachment made of a hardermaterial than the tibial template 2480. Upon fixing the position of thetibial template 2480, the cut guide of the tibial template 2475 assistsin guiding the desired cut on the tibia.

FIG. 26X shows a tibial template 2490 that may be used, after the tibialcut has been made, to further guide surgical tools in forming anchoringapertures in the tibia for utilization by the tibial implant (e.g., thetibial implant may include pegs and/or keels that are used to anchor thetibial implant into the tibia), in accordance with an embodiment of theinvention. The outer perimeter of a portion of the tibial template 2490may mimic the perimeter of the tibial implant. Guide apertures in thetibial template 2490 correspond to the tibial implants fixationfeatures. A portion of the tibial template 2490 conforms to, withoutlimitation, the anterior surface of the tibia to facilitate positioningand anchoring of the template 2490.

FIG. 26Y shows a tibial implant 2425 and femoral implant 2426 insertedonto the tibia and femur, respectively, after the above-described cutshave been made, in accordance with an embodiment of the invention.

Thus, the tibial template 2480 used on the tibia can be cross-referencedto the femoral template 2476, femoral cut and/or sample implant 2474.Similarly, in the hip, femoral templates can be placed in reference toan acetabular mold or vice versa. In general, when two or more articularsurfaces will be repaired or replaced, a template can be placed on oneor more of them and surgical procedures including cutting, drilling,sawing or rasping can be performed on the other surface or othersurfaces in reference to said first surface(s).

In illustrative embodiments, three-dimensional guidance templates may beutilized to determine an optimized implant rotation. Examples areprovided below with reference to the knee, however it is to beunderstood that optimizing implant rotation may be applied other jointsas well.

Femoral Rotation:

The optimal rotation of a femoral component or femoral implant for auni-compartmental, patello femoral replacement or total knee replacementmay be ascertained in a number of different ways. Implant rotation istypically defined using various anatomic axes or planes. These anatomicaxes may include, without limitation, the transepicondylar axis; theWhiteside line, i.e. the trochlea anteroposterior axis, which istypically perpendicular to at least one of the cuts; and/or theposterior condylar axis. Another approach for optimizing femoralcomponent rotation is a so-called balancing gap technique. With thebalancing gap technique, a femoral cut is made parallel to the tibia,i.e. the tibia is cut first typically. Prior to performing the femoralcut, the femoral cut plate is optimized so that the medial and lateralligament and soft tissue tension are approximately equal.

By measuring the relevant anatomic axis or planes, the optimal implantrotation may be determined. The measurement may be factored into theshape, position or orientation of the 3D guidance template, inaccordance with an embodiment of the invention. Any resultant surgicalinterventions including cuts, drilling, or sawings are then madeincorporating this measurement, thereby achieving an optimal femoralcomponent rotation.

Moreover in order to achieve an optimal balancing, the rotation of thetemplate may be changed so that the cuts are parallel to the tibial cutwith substantially equal tension medially and laterally applied.

Tibial Rotation:

A 3D guidance template may also be utilized to optimize tibial componentrotation for uni-compartmental or total knee replacements, in accordancewith an embodiment of the invention. Tibial component rotation may bemeasured using a number of different approaches known in the art. In oneexample of a tibial component rotation measurement, the anteroposterioraxis of the tibia is determined. For a total knee replacement, thetibial component can be placed so that the axis of the implant coincideswith the medial one-third of the tibial tuberosity. This approach workswell when the tibia is symmetrical.

In another embodiment, the symmetrical tibial component is placed as faras possible posterolateral and externally rotated so that theposteromedial corner of the tibial plateau is uncovered to an extent ofbetween three (3) and five (5) millimeters.

The above examples are only representative of the different approachesthat have been developed in the literature. Clearly, other variousanatomic axis, plane and area measurements may be performed in order tooptimize implant rotation.

In illustrative embodiments, these measurements may be factored into thedesign of a 3D guidance template and the position, shape or orientationof the 3D guidance template may be optimized utilizing this information.Thus, any subsequent surgical intervention such as cutting, sawingand/or drilling will result in an optimized implant rotation, forexample, in the horizontal or in a near horizontal plane.

Turning now to FIG. 27, a variety of illustrations are provided showinga patellar cutting block and mold system. FIGS. 27A-C illustrates thepatellar cutting block 2700 in conjunction with a patella 2702 that hasnot been resected. In this depiction, the cutting block 2700 can consistof only one piece or a plurality of pieces, if desired. The innersurface 2703 is patient specific and designed to mate, or substantiallymate, with the existing geography of the patient's patella 2702. Smallopenings are present 2707 to accept the saw. The mold or block can haveonly one or multiple openings. The openings can be larger than the sawin order to allow for some rotation or other fine adjustments. FIG. 27Ais a view in the sagittal plane S. The quadriceps tendon 2704 andpatellar tendon 2705 are shown.

FIG. 27B is a view in the axial plane A. The cartilage 2706 is shown.The mold can be molded to the cartilage or the subchondral bone orcombinations thereof. FIG. 27C is a frontal view F of the molddemonstrating the opening for the saw 2707. The dashed line indicatesthe relative position of the patella 2702.

FIGS. 27D (sagittal view) and E (axial view) illustrate a patellarcutting block 2708 in conjunction with a patella 2702 that has not beenresected. In this depiction, the cutting block 2708 consists of at leasttwo pieces. The first piece is a patient specific interior piece 2710 ormold that is designed on its inferior surface 2712 to mate, orsubstantially mate, with the existing geography of the patient's patella2702. The posterior surface 2714 and side surfaces 2716 of the firstpiece 2710 are configured to mate within the interior of an exteriorpiece 2720. The reusable exterior piece 2720 fits over the interiorpiece 2710 and holds it onto the patella. The reusable exterior piecehas an interior surface 2724 that mates with the first piece 2710. Thereusable exterior piece 2720 includes cutting guides 2707, to assist thesurgeon in performing the patellar surface cut. A plurality of cuttingguides can be provided to provide the surgeon a variety of locations tochoose from in making the patellar cut. If necessary, additional spacerscan be provided that fit between the first patient configured, ormolded, piece 2710 and the second reusable exterior piece, or cuttingblock, 2720.

The second reusable exterior piece, or cutting block, 2720, can havegrooves 2722 and extensions 2725 designed to mate with surgicalinstruments such as a patellar clamp 2726. The patellar clamp 2726 canhave ring shaped graspers 2728 and locking mechanisms, for exampleratchet-like 2730. The opening 2732 in the grasper fits onto theextension 2725 of the second reusable exterior piece 2720. Portions of afirst portion of the handle of the grasper can be at an oblique angle2734 relative to the second portion of the handle, or curved (notshown), in order to facilitate insertion. Typically the portion of thegrasper that will be facing towards the intra-articular side will havean oblique or curved shaped thereby allowing a slightly smallerincision.

The variable nature of the interior piece facilitates obtaining the mostaccurate cut despite the level of disease of the joint because itpositions the exterior piece 2720 in the desired plane. Either theinterior piece 2710 or the exterior piece 2720 can be formed out of anyof the materials discussed above in Section II, or any other suitablematerial. Additionally, a person of skill in the art will appreciatethat the invention is not limited to the two piece configurationdescribed herein. The reusable exterior piece 2720 and the patientspecific interior piece 2710 can be a single piece that is eitherpatient specific (where manufacturing costs of materials support such aproduct) or is reusable based on a library of substantially defectconforming shapes developed in response to known or common tibialsurface sizes and defects.

The interior piece 2710 is typically molded to the patella including thesubchondral bone and/or the cartilage.

From this determination, an understanding of the amount of space neededto balance the knee is determined and an appropriate number of spacersis then used in conjunction with the cutting block and mold to achievethe cutting surfaces and to prevent removal of too much bone. Where thecutting block has a thickness of, for example, 10 mm, and each spacerhas a thickness of 5 mm, in preparing the knee for cuts, two of thespacers would be removed when applying the cutting block to achieve thecutting planes identified as optimal during flexion and extension.Similar results can be achieved with ratchet or jack like designsinterposed between the mold and the cut guide.

vii. Hip Joint

Turning now to FIG. 28, a variety of views showing sample mold andcutting block systems for use in the hip joint are shown. FIG. 28Aillustrates femur 2510 with a mold and cutting block system 2520 placedto provide a cutting plane 2530 across the femoral neck 2512 tofacilitate removal of the head 2514 of the femur and creation of asurface 2516 for the hip ball prosthesis.

FIG. 28B illustrates a top view of the cutting block system 2520. Thecutting block system 2520 includes an interior, patient specific, moldedsection 2524 and an exterior cutting block surface 2522. The interior,patient specific, molded section 2524 can include a canal 2526 tofacilitate placing the interior section 2524 over the neck of the femur.As will be appreciated by those of skill in the art, the width of thecanal will vary depending upon the rigidity of the material used to makethe interior molded section. The exterior cutting block surface 2522 isconfigured to fit snugly around the interior section. Additionalstructures can be provided, similar to those described above withrespect to the knee cutting block system, that control movement of theexterior cutting block 2524 relative to interior mold section 2522, aswill be appreciated by those of skill in the art. Where the interiorsection 2524 encompasses all or part of the femoral neck, the cuttingblock system can be configured such that it aids in removal of thefemoral head once the cut has been made by, for example, providing ahandle 2501 as shown in FIG. 28G.

FIG. 28C illustrates a second cutting block system 2550 that can beplaced over the cut femur to provide a guide for reaming after thefemoral head has been removed using the cutting block shown in FIG. 28A.FIG. 28D is a top view of the cutting block shown in FIG. 28C. As willbe appreciated by those of skill in the art, the cutting block shown inFIG. 28C-D, can be one or more pieces. As shown in FIG. 28E, theaperture 2552 can be configured such that it enables the reaming for thepost of the implant to be at a 90° angle relative to the surface offemur. Alternatively, as shown in FIG. 28F, the aperture 2552 can beconfigured to provide an angle other than 90° for reaming, if desired.

FIGS. 29A (sagittal view) and 29B (frontal view, down onto mold)illustrates a mold system 2955 for the acetabulum 2957. The mold canhave grooves 2953 that stabilize it against the acetabular rim 2960.Surgical instruments, e.g. reamers, can be passed through an opening inthe mold 2956. The side wall of the opening 2962 can guide the directionof the reamer or other surgical instruments. Metal sleeves 2964 can beinserted into the side wall 2962 thereby protecting the side wall of themold from damage. The metal sleeves 2964 can have lips 2966 oroverhanging edges that secure the sleeve against the mold and help avoidmovement of the sleeve against the articular surface.

FIG. 29C is a frontal view of the same mold system shown in FIGS. 29Aand 29B. A groove 2970 has been added at the 6 and 12 o'clock positions.The groove can be used for accurate positioning or placement of surgicalinstruments. Moreover, the groove can be useful for accurate placementof the acetabular component without rotational error. Someone skilled inthe art will recognize that more than one groove or internal guide canbe used in order to not only reduce rotational error but also errorrelated to tilting of the implant. As seen FIG. 29D, the implant 2975can have little extensions 2977 matching the grooves thereby guiding theimplant placement. The extensions 2977 can be a permanent part of theimplant design or they can be detachable. Note metal rim 2979 and innerpolyethylene cup 2980 of the acetabular component.

FIG. 28H illustrates a cross-section of a system where the interiorsurface 2560 of the molded section 2524 has teeth 2562 or grooves tofacilitate grasping the neck of the femur.

Various steps may be performed in order to design and make 3D guidancetemplates for hip implants, in accordance with an embodiment of theinvention.

For example, in an initial step, a discrepancy in the length of the leftleg and right leg may be determined, for example, in millimeters. Leglength discrepancy may be determined, for example, using standingx-rays, typically including the entire leg but also cross-sectionalimaging modalities such as CT or MRI.

A CT scout scan may be utilized to estimate leg length. Alternatively,select image slices through the hip and ankle joint may be utilized toestimate leg length either using CT or MRI.

Pre-operative planning is then performed using the image data. A first3D guidance template is designed to rest on the femoral neck. FIG. 43shows an example of an intended site 4300 for placement of a femoralneck mold for total hip arthroplasty A cut or saw plane integrated intothis template can be derived. The position, shape and orientation of the3D guidance mold or jig or template may be determined on the basis ofanatomical axis such as the femoral neck axis, the biomechanical axisand/or also any underlying leg length discrepancy (FIG. 39).Specifically, the superoinferior cut or saw guide height can be adaptedto account for leg length discrepancy. For example, if the left leg isfive (5) millimeters shorter than the right leg, then the cut height canbe moved by five (5) millimeters to account for this difference. Thefemoral neck cut height ultimately determines the position of thefemoral stem. Thus, in this manner, using this type of pre-operativeplanning, the femoral neck cut height can be optimized using a 3Dguidance template.

FIG. 39 is a flow diagram of a method wherein measurement of leg lengthdiscrepancy can be utilized to determine the optimal cut height of thefemoral neck cut for total hip arthroplasty. Initially, imaging isperformed, e.g. CT and/or MRI, through, without limitation, the hip,knee and ankle joint, step 3902. Leg length discrepancy is determined,using the imaging data obtained, step 3904. The preferred implant sizemay then be optionally determined, step 3906. The preferred femoral neckcut position is determined based, at least in part, on correcting theleg length discrepancy for optimal femoral component placement.

FIG. 44 shows another example of a femoral neck mold 4400 with handle4410 and optional slot 4420.

Acetabulum:

In the acetabulum, the position and orientation of the acetabularcomponent or acetabular cup is also critical for the success of hipsurgery. For example, the lowest portion of the acetabular cup may beplaced so that it is five (5) millimeters lateral to an anatomiclandmark on a pelvic x-ray coinciding with the inferior border of theradiographic tear drop. If the acetabular component is, for example,placed too far superiorly, significant bone may be lost.

Placing the acetabular component using the 3D guidance template mayinclude, for example, the following steps:

Step One: Imaging, e.g. using optical imaging methods, CT or MRI.

Step Two: Determining the anterior rotation of the acetabulum and thedesired rotation of the acetabular cup.

Step Three: Find best fitting cup size.

Step Four: Determine optimal shape, orientation and/or position of 3Dguidance template.

The template may be optionally designed to rest primarily on the marginof the acetabular fossa. In this manner, it is possible to ream throughthe template.

FIG. 45 shows an example of a posterior acetabular approach for totalhip replacement. Tissue retractors 4510 are in place. The acetabularfossa is visible 4520.

FIG. 46 shows an example of a guidance mold used for reaming the sitefor an acetabular cup. The mold 4600 can be optionally attached to ageneric frame 4610. A guide for the reamer is shown 4620. The reamer4630 or the mold can have optional stops 4640. In this example, thestops 4640 are attached to the reamer 4630 and engage the guide 4620 forthe reamer.

For purposes of reaming, the template may be fixed to the pelvis, forexample, using metal spikes or K-wires. The template may also have agrip for fixing it to the bone. Thus, a surgeon may optionally press thetemplate against the bone while a second surgeon will perform thereaming through the opening in the template. The grip or any stabilizerscan extend laterally, and optionally serve as tissue retractors, keepingany potentially interfering soft tissue out of the surgical field. Thetemplate may also include stoppers 4640 to avoid over penetration of thereamer. These stoppers may be designed in the form of metal stopsdefining the deepest penetration area for the peripheral portion orother portions of the reamer. Optionally, the template may also taperand decrease in inner radius thereby creating a stop once the reameronce the reaches the innermost portion of the template. Any stop knownin the art can be used. The imaging test can be used to design or shapethe mold in a manner that will help achieve the optimal reaming depth.The stops can be placed on the mold or reamer in reference to theimaging test in order to achieve the optional reaming depth.

A 3D guidance template may be utilized to optimize the anteversion ofthe acetabular cup. For example, with the posteral lateral approach,typically an anteversion of forty to forty-five degrees is desired inboth males and females. With an anterolateral approach, zero degreesanteversion may be desired. Irrespective of the desired degree ofanti-version, the shape, orientation and/or position of the template maybe optimized to include the desired degree of anteversion.

Similarly, on the femoral side, the 3D guidance template may beoptimized with regard to its shape, orientation and position in order toaccount for neutral, varus or valgus position of the femoral shaft. A 3Dguidance template may also be utilized to optimize femoral shaftanteversion.

Thus, after a first template has been utilized for performing thefemoral neck cut and a second template has been utilized for performingthe surgical intervention on the acetabular side, a third template mayoptionally be utilized to be placed onto the femoral cut.

FIG. 47 shows an example of an optional third mold 4700, placed on thefemoral neck cut, providing and estimate of anteversion and longitudinalfemoral axis.

The third template may optionally include a handle. The third templatemay be shaped, designed, oriented and/or positioned so that it isoptimized to provide the surgeon with information and reference pointsfor the long axis of the femur 4710 and femoral anteversion 4720. Abroach 4730 with broach handle 4740 is seen in place. The cut femoralneck 4750 is seen. The third mold 4700 attaches to it. By providinginformation on the long axis of the femur and femoral anteversion, anintra-operative x-ray can be saved which would otherwise be necessitatedin order to obtain this information.

Optionally, modular hip implant components may be utilized such as amodular stem. Such modular designs can be helpful in further optimizingthe resultant femoral anteversion by selecting, for example, differentstem shapes.

In another embodiment, the surgeon may perform a femur first techniquewherein a first cut is applied to the femur using a first 3D guidancemold. Optionally, the broach in the cut femoral shaft may be left inplace. Optionally, a trial implant head may be applied to the broach.The trial implant head may be variable in radius and superoinferiordiameter and may be utilized to determine the optimal soft tissuetension. Optionally, the trial head may also be utilized to determinethe acetabular cup position wherein said acetabular cup position isderived on the basis of the femoral cut. Thus, the acetabular positioncan be optionally derived using the opposite articular surface. In areverse acetabulum first technique, the acetabulum can be prepared firstand, using soft tissue balancing techniques, the femoral component canbe placed in reference to the acetabular component. Optionally, thefemoral cut may even be placed intentionally too proximal and issubsequently optimized by measuring soft tissue tension utilizingvarious trial heads with the option to then change the height of theoptimal femoral cut.

Positioning of Template

In an illustrative embodiment of the invention, in order to make aguidance template reliably and reproducibly, a portion of the joint isidentified in a first step wherein said portion of the joint has notbeen altered by the arthritic process. In a second step, the surface ora point cloud of said portion of the joint is derived, and may,optionally, be used to derive a virtual 3D model and, in a third step,to generate a physical model as part of the guidance template. Using aportion of the joint that has not been altered by the arthritic processcan advantageously improve the reproducibility and the accuracy of theresultant mold or jig or template.

The step of identifying said portion of the joint may be visual,semiautomatic or fully automatic. Anatomic models may assist in theprocess. Anatomic reference standards may be utilized.

As known in the art, various methods for image segmentation may be usedto derive the point cloud or the surface. Suitable algorithms include,for example, but are not limited to snakes, live wire, thresholding,active contours, deformable models and the like. Artificial neuralnetworks may be employed to improve the accuracy of the molds.

In another embodiment, the current biomechanical axis may determined orestimated in a first step. In a second step, the desired biomechanicalaxis is determined. In a third step adjustments, for example via changein slot position or position for openings for saws and drills and thelike, may be made to alter the cut or drill position in order to correctthe biomechanical axis in a fourth step. In a fifth step, the positionof the slot or openings for saws and drills and the like may be adjustedfor ligament balancing and/or for optimizing flexion and extension gap.This adjustment may be performed in the 3D model prior to themanufacturing process. Alternatively, adjustments may be madeintraoperatively, for example via spacers or ratchet like devices orpins to allow for some degree of rotation.

In another embodiment, at least a portion of the surface of the mold orjig or template is derived from a portion of the joint that is affectedby the arthritic process. Optionally, adjustment means can be performed,for example via the software, to simulate a normal shape. The differencebetween the actual shape and the adjusted shape can be utilized theoptimize the position of the slots or openings in the mold or templateor jig.

In a preferred embodiment, at least a portion of the surface of the moldor jig or template that is in contact with the joint may be derived froma portion of the joint that is affected by the arthritic process and aportion of the joint that has not been altered by the arthritic process.By spanning both normal and diseased portions of the joint, theinterface between normal and diseased portions of the joint is includedin the surface of the mold. The interface between normal and diseasedportions of the joint is typically characterized by a sudden change incontour or shape, e.g. a reduction in cartilage thickness, a change insubchondral bone contour, a cyst or a bone spur. This change in jointcontour or shape provides additional reference points for accuratelyplacing the mold or jig or template. In addition, this change in jointcontour or shape provides also additional stabilization or fixation ofthe mold or jig or template on the surface of the joint, in particularwhile performing surgical interventions such as cutting, drilling orsawing.

viii. Patellar Template

FIG. 48A illustrates a patella 4800 having a patellar ridge 4802,patellar facets 4804, 4804. Also depicted are the superior 4810,inferior 4812, lateral 4814, and medial 4816 surfaces.

FIG. 48B illustrates a mold drill guide 4820 from the perspective of thepatella matching surface 4822. The mold drill guide 4820 is configuredso that it is substantially a round cylinder. However, other shapes canbe employed without departing from the scope of the invention. Suchshapes can be strictly geometrical, e.g. ovoid, or non-geometrical.

The patella matching surface 4822 has an articular surfaces thatmatches, or closely conforms to, the surface of the patella. The designis proposed such that the guide is molded to precisely fit the anatomyof the articular surface of the patella for each patient, thus providingprecise location of the patella planing needed. As will be appreciatedby those of skill in the art, while an exact or precise fit is desired,deviations from a precise fit can occur without departing from the scopeof the invention. Thus, it is anticipated that a certain amount of errorin the design can be tolerated.

FIG. 48C illustrates the guide 4820 from the opposite perspective. Theplanar guide surface or element 4824 is depicted as flat, orsubstantially flat. However, as will be appreciated by those of skill inthe art, other surface configurations can be employed without departingfrom the scope of the invention. Both FIGS. 48A and B depict apertures4830, 4832. A central aperture 4830 is provided that accommodates, forexample, a ⅛ drill bit. The central aperture 4830 can be located suchthat it is centered within the guide, off-centered, or slightlyoff-centered, without departing from the scope of the invention. Anoff-center or slightly off-center configure could be used with the roundcylindrical configuration, but could also be used with the otherconfigurations as well. One or more additional apertures 4832 can beprovided to enable peg holes to be drilled. The apertures 4832 can beconfigured to have a larger diameter as the first aperture 4830, asmaller diameter, or an identical diameter.

As shown in FIG. 48D the mold drill guide is fitted onto the articularsurface of the patella. Because the articular facing surface (shown inFIG. 48A) is configured to match or substantially match the articularsurface of the patella, the drill guide mates with the patellar surfaceto enable the drill holes to line-up in the desired place for theimplant. FIG. 48E illustrates the mold drill guide fitted onto thearticular surface of the patella with a ⅛″ drill 4850 positioned withinthe central aperture 4830.

Once a central aperture 4818 has been formed into the patella, a patellareamer 4860 is used to resurface the patella 4800. The reamer 4860 has aguide 4862, which fits within the aperture 4818, and a reamer 4864having a planing surface or blade surface 1066.

Turning to FIG. 49A the reamer 1060 is shown. The planing surface 1066has is configured to provide dual planing surfaces in order to recessthe patella and clear surrounding bone. Providing dual planing surfaceshelps to insure poly-metal articulation only. FIG. 49B illustrates thereamer relative to a patella. An area is prepared 1062 for a 30 mmpatella insert, and a surrounding area 1061 is reamed.

FIG. 50A illustrates a patella implant 5000. The inferior surface of theimplant 5000, has one or more pegs 5010. In this instance, the inferiorsurface 5002 is depicted with three pegs 5010. The implant 5000 ispositioned on a patella as shown in FIG. 50C such that a protuberance5020 on the superior surface 5004 of the implant is positionedapproximately at the apex of the natural patella. FIGS. 50D-F illustratethe implant superimposed within a patella, more clearly showing theprotuberance corresponding to the apex of the natural patella.

B. Small, Focal Cartilage Defect

After identification of the cartilage defect and marking of the skinsurface using the proprietary U-shaped cartilage defect locator deviceas described herein, a 3 cm incision is placed and the tissue retractorsare inserted. The cartilage defect is visualized.

A first Lucite block matching the 3D surface of the femoral condyle isplaced over the cartilage defect. The central portion of the Luciteblock contains a drill hole with an inner diameter of, for example, 1.5cm, corresponding to the diameter of the base plate of the implant. Astandard surgical drill with a drill guide for depth control is insertedthrough the Lucite block, and the recipient site is prepared for thebase component of the implant. The drill and the Lucite block are thenremoved.

A second Lucite block of identical outer dimensions is then placed overthe implant recipient site. The second Lucite block has a rounded,cylindrical extension matching the size of the first drill hole (andmatching the shape of the base component of the implant), with adiameter 0.1 mm smaller than the first drill hole and 0.2 mm smallerthan that of the base of the implant. The cylindrical extension isplaced inside the first drill hole.

The second Lucite block contains a drill hole extending from theexternal surface of the block to the cylindrical extension. The innerdiameter of the second drill hole matches the diameter of the distalportion of the fin-shaped stabilizer strut of the implant, e.g. 3 mm. Adrill, e.g. with 3 mm diameter, with a drill guide for depth control isinserted into the second hole and the recipient site is prepared for thestabilizer strut with a four fin and step design. The drill and theLucite block are then removed.

A plastic model/trial implant matching the 3-D shape of the finalimplant with a diameter of the base component of 0.2 mm less than thatof the final implant and a cylindrical rather than tapered strutstabilizer with a diameter of 0.1 mm less than the distal portion of thefinal implant is then placed inside the cartilage defect. The plasticmodel/trial implant is used to confirm alignment of the implant surfacewith the surrounding cartilage. The surgeon then performs finaladjustments.

The implant is subsequently placed inside the recipient site. Theanterior fin of the implant is marked with red color and labeled “A.”The posterior fin is marked green with a label “P” and the medial fin iscolor coded yellow with a label “M.” The Lucite block is then placedover the implant. A plastic hammer is utilized to advance the implantslowly into the recipient site. A press fit is achieved with help of thetapered and four fin design of the strut, as well as the slightlygreater diameter (0.1 mm) of the base component relative to the drillhole. The Lucite block is removed. The tissue retractors are thenremoved. Standard surgical technique is used to close the 3 cm incision.The same procedure described above for the medial femoral condyle canalso be applied to the lateral femoral condyle, the medial tibialplateau, the lateral tibial plateau and the patella. Immediatestabilization of the device can be achieved by combining it with bonecement if desired.

IV. Kits

Also described herein are kits comprising one or more of the methods,systems and/or compositions described herein. In particular, a kit caninclude one or more of the following: instructions (methods) ofobtaining electronic images; systems or instructions for evaluatingelectronic images; one or more computer means capable of analyzing orprocessing the electronic images; and/or one or more surgical tools forimplanting an articular repair system. The kits can include othermaterials, for example, instructions, reagents, containers and/orimaging aids (e.g., films, holders, digitizers, etc.).

The following examples are included to more fully illustrate the presentinvention. Additionally, these examples provide preferred embodiments ofthe invention and are not meant to limit the scope thereof.

Example 1 Design and Construction of a Three-Dimensional ArticularRepair System

Areas of cartilage are imaged as described herein to detect areas ofcartilage loss and/or diseased cartilage. The margins and shape of thecartilage and subchondral bone adjacent to the diseased areas aredetermined. The thickness of the cartilage is determined. The size ofthe articular repair system is determined based on the abovemeasurements. (FIGS. 12-14). In particular, the repair system is eitherselected (based on best fit) from a catalogue of existing, pre-madeimplants with a range of different sizes and curvatures orcustom-designed using CAD/CAM technology. The library of existing shapesis typically on the order of about 30 sizes.

The implant is a chromium cobalt implant (see also FIGS. 12-14 and17-19). The articular surface is polished and the external dimensionsslightly greater than the area of diseased cartilage. The shape isadapted to achieve perfect or near perfect joint congruity utilizingshape information of surrounding cartilage and underlying subchondralbone. Other design features of the implant can include: a slanted (60-to 70-degree angle) interface to adjacent cartilage; a broad-based basecomponent for depth control; a press fit design of base component; aporous coating of base component for ingrowth of bone and rigidstabilization; a dual peg design for large defects implantstabilization, also porous coated (FIG. 12A); a single stabilizer strutwith tapered, four fin and step design for small, focal defects, alsoporous coated (FIG. 12B); and a design applicable to femoral resurfacing(convex external surface) and tibial resurfacing (concave externalsurface).

Example 2 Minimally Invasive, Arthroscopically Assisted SurgicalTechnique

The articular repair systems are inserted using arthroscopic assistance.The device does not require the 15 to 30 cm incision utilized inunicompartmental and total knee arthroplasties. The procedure isperformed under regional anesthesia, typically epidural anesthesia. Thesurgeon can apply a tourniquet on the upper thigh of the patient torestrict the blood flow to the knee during the procedure. The leg isprepped and draped in sterile technique. A stylette is used to createtwo small 2 mm ports at the anteromedial and the anterolateral aspect ofthe joint using classical arthroscopic technique. The arthroscope isinserted via the lateral port. The arthroscopic instruments are insertedvia the medial port. The cartilage defect is visualized using thearthroscope. A cartilage defect locator device is placed inside thediseased cartilage. The probe has a U-shape, with the first arm touchingthe center of the area of diseased cartilage inside the joint and thesecond arm of the U remaining outside the joint. The second arm of the Uindicates the position of the cartilage relative to the skin. Thesurgeon marks the position of the cartilage defect on the skin. A 3 cmincision is created over the defect. Tissue retractors are inserted andthe defect is visualized.

A translucent Lucite block matching the 3D shape of the adjacentcartilage and the cartilage defect is placed over the cartilage defect(FIG. 13). For larger defects, the Lucite block includes a lateral slotfor insertion of a saw. The saw is inserted and a straight cut is madeacross the articular surface, removing an area slightly larger than thediseased cartilage. The center of the Lucite block contains two drillholes with a 7.2 mm diameter. A 7.1 mm drill with drill guidecontrolling the depth of tissue penetration is inserted via the drillhole. Holes for the cylindrical pegs of the implant are created. Thedrill and the Lucite block are subsequently removed.

A plastic model/trial implant of the mini-repair system matching theouter dimensions of the implant is then inserted. The trial implant isutilized to confirm anatomic placement of the actual implant. Ifindicated, the surgeon can make smaller adjustments at this point toimprove the match, e.g. slight expansion of the drill holes oradjustment of the cut plane.

The implant is then inserted with the pegs pointing into the drillholes. Anterior and posterior positions of the implant are color-coded;specifically the anterior peg is marked with a red color and a smallletter “A”, while the posterior peg has a green color and a small letter“P”. Similarly, the medial aspect of the implant is color-coded yellowand marked with a small letter “M” and the lateral aspect of the implantis marked with a small letter “L”. The Lucite block is then placed onthe external surface of the implant and a plastic hammer is used togently advance the pegs into the drill holes. The pegs are designed toachieve a press fit.

The same technique can be applied in the tibia. The implant has aconcave articular surface matching the 3D shape of the tibial plateau.Immediate stabilization of the device can be achieved by combining itwith bone cement if desired.

The foregoing description of embodiments of the present invention hasbeen provided for the purposes of illustration and description. It isnot intended to be exhaustive or to limit the invention to the preciseforms disclosed. Many modifications and variations will be apparent tothe practitioner skilled in the art. The embodiments were chosen anddescribed in order to best explain the principles of the invention andits practical application, thereby enabling others skilled in the art tounderstand the invention and the various embodiments and with variousmodifications that are suited to the particular use contemplated. It isintended that the scope of the invention be defined by the followingclaims equivalents thereof.

What is claimed is:
 1. A method of surgically repairing, replacing orresurfacing a hip joint of a patient, comprising: placing apatient-specific surface of a surgical instrument on a correspondingsurface portion of a hip joint of a patient to define a predeterminedguide path relative to an axis of the hip joint extending through afemoral neck of the hip joint of the patient, wherein at least a portionof the patient-specific surface has a shape that substantially matches ashape of the corresponding surface portion of the hip joint and thepatient-specific surface and a position and/or orientation of the guidepath are each configured based at least in part on image data of the hipjoint of the patient; removing tissue along the guide path; andimplanting a prosthesis at a site associated with the removed tissue. 2.The method of claim 1, wherein the guide path extends along at least aportion of the axis.
 3. The method of claim 1, wherein the guide pathextends along at least a portion of a femoral neck axis.
 4. A method ofsurgically repairing, replacing or resurfacing a hip joint of a patient,comprising: placing a patient-specific surface of a surgical instrumenton a corresponding cartilage surface portion of a hip joint of a patientto position a guide configured to provide a guide path in apredetermined location and/or orientation relative to the cartilagesurface of the hip joint, wherein at least a portion of thepatient-specific surface has a shape that substantially matches a shapeof the corresponding cartilage surface portion of the hip joint andwherein the patient-specific surface and the location and/or orientationof the guide path are each configured based at least in part on imagedata of the hip joint of the patient; using the guide to surgicallyalter the proximal femur by cutting, drilling or reaming tissue of theproximal end of the femur; and implanting a prosthesis having a locationbased at least in part on the location of the cut, drilled or reamedtissue.
 5. A method of surgically repairing, replacing or resurfacing ahip joint of a patient, comprising: placing a patient-specific surfaceof a surgical instrument on a corresponding femoral surface portion of ahip joint of a patient to position a guide configured to provide a guidepath in a predetermined location and/or orientation relative to thecorresponding femoral surface of the hip joint, wherein at least aportion of the patient-specific surface has a shape that substantiallymatches a shape of the corresponding femoral surface portion of the hipjoint and the patient-specific surface and the location and/ororientation of the guide path are each configured based at least in parton image data of the hip joint of the patient; guiding a surgical toolwith the guide to surgically alter tissue of the hip joint; andorienting at least one component of a hip prosthesis based at least inpart on the location of the guide.
 6. The method of claim 5, wherein thestep of guiding a surgical tool to surgically alter tissue of the hipjoint includes at least one of cutting, drilling and reaming the tissue.7. The method of claim 5, wherein the step of orienting at least onecomponent of a hip prosthesis comprises establishing a predeterminedanteversion of the at least one component.
 8. The method of claim 5,wherein the step of orienting at least one component of a hip prosthesiscomprises establishing a predetermined retroversion of the at least onecomponent.
 9. The method of claim 5, wherein the step of orienting atleast one component of a hip prosthesis comprises establishing apredetermined rotation of the at least one component.
 10. The method ofclaim 5, wherein the step of orienting at least one component of a hipprosthesis comprises establishing a predetermined tilt of the at leastone component.
 11. The method of claim 5, wherein the step of orientingat least one component of a hip prosthesis comprises orienting anacetabular component.
 12. The method of claim 5, wherein the step oforienting at least one component of a hip prosthesis comprises orientingan acetabular cup.
 13. The method of claim 5, wherein the step oforienting at least one component of a hip prosthesis comprises orientinga femoral component.
 14. The method of claim 5, wherein the step oforienting at least one component of a hip prosthesis comprises orientinga femoral head component.
 15. A method of surgically repairing,replacing or resurfacing a hip joint of a patient, comprising: placing apatient-specific surface of a surgical instrument on a correspondingsurface portion of an acetabulum of a hip joint of a patient to positiona guide configured to provide a guide path in a predetermined locationand/or orientation relative to the acetabulum of the hip joint, whereinat least a portion of the patient-specific surface has a shape thatsubstantially matches a shape of the corresponding surface portion ofthe acetabulum of the hip joint and the patient-specific surface and thelocation and/or orientation of the guide path are each configured basedat least in part on image data of the hip joint of the patient, whereinthe corresponding surface portion of the acetabulum of the hip jointincludes a surface portion selected from the group consisting of: anacetabular wall surface portion, an acetabular rim surface portion; anacetabular fossa surface portion, and any combination thereof; guiding asurgical tool with the guide to surgically alter tissue of the hipjoint; and implanting a hip joint prosthesis having a location based atleast in part on the location of the surgically altered tissue.
 16. Themethod of claim 15, wherein the step of guiding a surgical tool tosurgically alter tissue of the hip joint includes at least one ofcutting, drilling and reaming the tissue.
 17. The method of claim 15,wherein the corresponding surface of the acetabulum includes at least aportion of a cartilage surface of the acetabulum.
 18. The method ofclaim 15, wherein the corresponding surface of the acetabulum includesat least a portion of a subchondral bone surface of the acetabulum. 19.The method of claim 15, wherein the corresponding surface of theacetabulum includes at least a portion of a cortical bone surface of theacetabulum.
 20. The method of claim 15, wherein the correspondingsurface of the acetabulum includes at least a portion of an osteophyteof the acetabulum.
 21. A method of surgically repairing, replacing orresurfacing a hip joint of a patient, comprising: placing apatient-specific surface of a surgical instrument on a correspondingsurface portion of a proximal end of a femur of a hip joint of a patientto position a guide configured to provide a guide path in apredetermined location and/or orientation relative to the proximal endof the femur of the hip joint, wherein at least a portion of thepatient-specific surface has a shape that substantially matches a shapeof the corresponding surface portion of the proximal end of the femur ofthe hip joint and the patient-specific surface and the location and/ororientation of the guide path are each based at least in part on imagedata of the hip joint of the patient; guiding a surgical tool with theguide to surgically alter tissue of the hip joint; and implanting a hipjoint prosthesis having a location based at least in part on thelocation of the surgically altered tissue.
 22. The method of claim 21,wherein the step of guiding a surgical tool to surgically alter tissueof the hip joint includes at least one of cutting, drilling and reamingthe tissue.
 23. The method of claim 21, wherein the correspondingsurface of the proximal end of the femur includes at least a portion ofa femoral neck of the femur.
 24. The method of claim 21, wherein thecorresponding surface of the proximal end of the femur includes at leasta portion of a femoral head of the femur.
 25. The method of claim 21,wherein the corresponding surface of the proximal end of the femurincludes at least a portion of a junction of a femoral neck and afemoral head of the femur.
 26. The method of claim 21, wherein thecorresponding surface of the proximal end of the femur includes at leasta portion of a cartilage surface of the femur.
 27. The method of claim21, wherein the corresponding surface of the proximal end of the femurincludes at least a portion of a subchondral bone surface of the femur.28. The method of claim 21, wherein the corresponding surface of theproximal end of the femur includes at least a portion of a cortical bonesurface of the femur.
 29. The method of claim 21, wherein thecorresponding surface of the proximal end of the femur includes at leasta portion of an osteophyte of the femur.
 30. A method of surgicallyrepairing, replacing or resurfacing a hip joint of a patient,comprising: placing a patient-specific surface of a surgical instrumenton a corresponding surface portion of a femoral neck of a hip joint of apatient to position a guide configured to provide a guide path in apredetermined location and/or orientation relative to a femur of the hipjoint, wherein at least a portion of the patient-specific surface has ashape that substantially matches a shape of the corresponding surfaceportion of the femoral neck; resecting the femoral neck based at leastin part on the location of the guide; and implanting a prosthesis basedat least in part on the location of the resected tissue.
 31. The methodof claim 30, wherein the guide path is configured to extend through thefemoral neck and the femoral shaft, and wherein the step of resectingfurther comprises directing a surgical tool along the guide to resectthe femoral neck.
 32. A method of surgically repairing, replacing orresurfacing a hip joint of a patient, comprising: placing apatient-specific surface of a surgical instrument on a correspondingfemoral surface portion of a hip joint of a patient to define apredetermined guide path relative to an axis of the hip extendingthrough a femoral head of the patient, wherein at least a portion of thepatient-specific surface has a shape that substantially matches a shapeof the corresponding femoral surface portion of the hip joint and thepatient-specific surface and the guide path are each configured based atleast in part on image data of the hip joint of the patient; removingtissue along the guide path; and implanting a prosthesis at the site ofthe removed tissue.
 33. The method of claim 32, wherein the guide pathextends along at least a portion of the axis.
 34. The method of claim32, wherein the guide path extends along at least a portion of a femoralhead axis.
 35. The method of claim 32, wherein the guide path extendsalong at least a portion of a femoral neck axis.
 36. The method of claim32, wherein the guide path extends along at least a portion of a femoralshaft axis.
 37. A method of surgically repairing, replacing orresurfacing a hip joint of a patient, comprising: placing apatient-specific surface of a surgical instrument on a correspondingfemoral surface portion of a hip joint of a patient to define apredetermined guide path relative to an axis of the hip extendingthrough a femoral shaft of the patient, wherein at least a portion ofthe patient-specific surface has a shape that substantially matches ashape of the corresponding femoral surface portion of the hip joint andthe patient-specific surface and the guide path are each configuredbased at least in part on image data of the hip joint of the patient;removing tissue along the guide path; and implanting a prosthesis at thesite of the removed tissue.
 38. The method of claim 37, wherein theguide path extends along at least a portion of the axis.
 39. The methodof claim 37, wherein the guide path extends along at least a portion ofa femoral head axis.
 40. The method of claim 37, wherein the guide pathextends along at least a portion of a femoral neck axis.
 41. The methodof claim 37, wherein the guide path extends along at least a portion ofa femoral shaft axis.